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1

Cross-beta-sheet structure in amyloid fiber formation.  

PubMed

As proteins aggregate to form amyloid fibers, their secondary structure changes from its native form to cross-beta-sheet. Whether this conformational change is essential for fiber formation remains unknown. Evidence from atomic force microscopy and transmission electron microscopy suggests that aggregation occurs in two stages. Initially, protein monomers aggregate into colloidal spheres; however, they stop growing after reaching a uniform diameter. The spheres then join together to form linear chains which evolve into mature fibers. In this paper, we apply, for the first time, the DLVO theory, formulated by Derjaguin, Landau, Verwey and Overbeek for the quantitative analysis of colloidal interactions, to elucidate the two stages of fiber formation. We find that, as like-charged protein molecules aggregate, the total charge of the colloidal sphere increases until it repels additional monomers from coming close enough to bind, limiting the size of the colloidal particle. Energy analysis and X-ray diffraction data suggest that aggregation of multiple protein monomers onto the growing colloid drives their misfolding into hairpin loops. These loops stack together to form a U-shaped trough which initially adopts a cross-alpha-sheet structure with a strong dipole moment. Driven by charge-dipole interactions, the colloidal spheres aggregate into a linear chain. The peptide strands are oriented perpendicular to the direction of the dipole of each sphere and, therefore, are also perpendicular to the axis of the linear chain as it forms and evolves into the mature fiber. The cross alpha-sheet then evolves into the thermodynamically more stable cross beta-sheet. PMID:19705845

Xu, Shaohua

2009-09-17

2

Free energy determinants of secondary structure formation: II. Antiparallel beta-sheets.  

PubMed

The factors that determine the stability of antiparallel beta-sheets are considered via a theoretical analysis of conformational free energies. A series of idealized model polyalanine beta-sheets are built with constraints such that the angular geometry of hydrogen bonding varies in the range observed in proteins while hydrogen bonding distance remains fixed. The conformations of the sheets generated in this way have a broad distribution of twist angles ranging from highly twisted left-handed to highly twisted right-handed orientations. The association free energies of the sheets are calculated with a gas phase CHARMM potential and FDPB/gamma solvation models. Left-handed structures are found to be less stable than right handed structures due to intrachain steric hindrance in isolated left-handed strands. This explains why antiparallel beta-sheets in proteins are invariably twisted in the right-handed direction. The free energy surface for right-handed sheets shows particular preference for conformations ranging from flat to those that exhibit a pronounced right-handed twist. This suggests that antiparallel beta-sheets can adopt a variety of right-handed conformations, a result that is consistent with observations on known proteins. In parallel with our study of alpha-helices we find that van der Waals and hydrophobic interactions are the primary factor stabilizing polyalanine beta-sheets, while electrostatic interactions including hydrogen bonding are found to be destabilizing. However, in contrast to helices, the net change in conformational free energy involving only backbone-backbone interactions (including beta-carbons) is not sufficient to overcome the loss in configurational entropy that accompanies sheet formation. Rather we suggest that cross-strand non-polar side-chain-side-chain interactions are essential for sheet formation, explaining why large non-polar amino acids have the greatest sheet forming propensities. Thus, sheet propensities involve pairwise interactions and are expected to be context dependent, as has been observed in recent experiments. PMID:7563057

Yang, A S; Honig, B

1995-09-22

3

Conformational diversity in prion protein variants influences intermolecular [beta]-sheet formation  

SciTech Connect

A conformational transition of normal cellular prion protein (PrP{sup C}) to its pathogenic form (PrP{sup Sc}) is believed to be a central event in the transmission of the devastating neurological diseases known as spongiform encephalopathies. The common methionine/valine polymorphism at residue 129 in the PrP influences disease susceptibility and phenotype. We report here seven crystal structures of human PrP variants: three of wild-type (WT) PrP containing V129, and four of the familial variants D178N and F198S, containing either M129 or V129. Comparison of these structures with each other and with previously published WT PrP structures containing M129 revealed that only WT PrPs were found to crystallize as domain-swapped dimers or closed monomers; the four mutant PrPs crystallized as non-swapped dimers. Three of the four mutant PrPs aligned to form intermolecular {beta}-sheets. Several regions of structural variability were identified, and analysis of their conformations provides an explanation for the structural features, which can influence the formation and conformation of intermolecular {beta}-sheets involving the M/V129 polymorphic residue.

Lee, Seungjoo; Antony, Lizamma; Hartmann, Rune; Knaus, Karen J.; Surewicz, Krystyna; Surewicz, Witold K.; Yee, Vivien C. (Case Western); (Cleveland Clinic)

2010-04-19

4

Modulation of fibril formation by a beta-sheet breaker peptide ligand: An electrochemical approach  

Microsoft Academic Search

The development of generic inhibitors in order to control the formation of amyloid fibrils and early oligomers is still an unmet medical need. Here, we demonstrate the applicability of electrochemical analysis for the detection of ?-sheet breaker peptide ligands that act as excellent inhibitors of Alzheimer's disease (AD) amyloid-? (A?) fibrils and oligomers in vitro. As the case study, a

Anthony J. Veloso; Kagan Kerman

5

Singular points of protein beta-sheets.  

PubMed Central

Protein beta-sheets can be regarded as surfaces. Two surfaces can be connected along a common edge to form a larger surface, or two edges of a surface can coalesce to form a closed sheet such as a beta-barrel. Singular points are locations where these connections are not perfect. In protein beta-sheets, a singular point is characterized by a residue separating two beta-ladders. In this paper, we study the singular points of protein beta-sheets from the surface topologic viewpoint, summarize our search results from the protein structural data in the Protein Data Bank, and present examples where singular points are near the active sites and may contribute to forming the proper relative positions of catalytic residues. PMID:9827998

Liu, W. M.; Chou, K. C.

1998-01-01

6

Sequence specificity, statistical potentials, and three-dimensional structure prediction with self-correcting distance geometry calculations of beta-sheet formation in proteins.  

PubMed Central

A statistical analysis of a representative data set of 169 known protein structures was used to analyze the specificity of residue interactions between spatial neighboring strands in beta-sheets. Pairwise potentials were derived from the frequency of residue pairs in nearest contact, second nearest and third nearest contacts across neighboring beta-strands compared to the expected frequency of residue pairs in a random model. A pseudo-energy function based on these statistical pairwise potentials recognized native beta-sheets among possible alternative pairings. The native pairing was found within the three lowest energies in 73% of the cases in the training data set and in 63% of beta-sheets in a test data set of 67 proteins, which were not part of the training set. The energy function was also used to detect tripeptides, which occur frequently in beta-sheets of native proteins. The majority of native partners of tripeptides were distributed in a low energy range. Self-correcting distance geometry (SECODG) calculations using distance constraints sets derived from possible low energy pairing of beta-strands uniquely identified the native pairing of the beta-sheet in pancreatic trypsin inhibitor (BPTI). These results will be useful for predicting the structure of proteins from their amino acid sequence as well as for the design of proteins containing beta-sheets. PMID:10048326

Zhu, H.; Braun, W.

1999-01-01

7

Amyloid Beta Mediates Memory Formation  

ERIC Educational Resources Information Center

The amyloid precursor protein (APP) undergoes sequential cleavages to generate various polypeptides, including the amyloid [beta] (1-42) peptide (A[beta][1-42]), which is believed to play a major role in amyloid plaque formation in Alzheimer's disease (AD). Here we provide evidence that, in contrast with its pathological role when accumulated,…

Garcia-Osta, Ana; Alberini, Cristina M.

2009-01-01

8

Bayesian Models and Algorithms for Protein Beta-Sheet Prediction  

E-print Network

diseases, including Alzheimer's and mad cow diseases [1]. -sheets can be open, meaning that they have two of -sheets has been implicated in the forma- tion of protein aggregates and fibrils observed in many human. As the fourth com- ponent of the -sheet formation, a contact map defines the amino acid pairs that make non

Erdogan, Hakan

9

Cooperative deformation of hydrogen bonds in beta-strands and beta-sheet nanocrystals  

E-print Network

Beta-sheet protein domains are stabilized by weak hydrogen bonds, yet materials such as silk—whose ultimate tensile strength is controlled primarily by this secondary structure—can exceed the ultimate tensile strength of ...

Qin, Zhao

10

Role of Polyalanine Domains in -Sheet Formation in Spider Silk Block Copolymers  

SciTech Connect

Genetically engineered spider silk-like block copolymers were studied to determine the influence of polyalanine domain size on secondary structure. The role of polyalanine block distribution on {beta}-sheet formation was explored using FT-IR and WAXS. The number of polyalanine blocks had a direct effect on the formation of crystalline {beta}-sheets, reflected in the change in crystallinity index as the blocks of polyalanines increased. WAXS analysis confirmed the crystalline nature of the sample with the largest number of polyalanine blocks. This approach provides a platform for further exploration of the role of specific amino acid chemistries in regulating the assembly of {beta}-sheet secondary structures, leading to options to regulate material properties through manipulation of this key component in spider silks.

Rabotyagova, O.; Cebe, P; Kaplan, D

2010-01-01

11

Formation of Sprays From Conical Liquid Sheets  

NASA Technical Reports Server (NTRS)

Our objective is to predict droplet size distributions created by fuel injector nozzles in Jet turbines. These results will be used to determine the initial conditions for numerical simulations of the combustion process in gas turbine combustors. To predict the droplet size distribution, we are currently constructing a numerical model to understand the instability and breakup of thin conical liquid sheets. This geometry serves as a simplified model of the liquid jet emerging from a real nozzle. The physics of this process is difficult to study experimentally as the time and length scales are very short. From existing photographic data, it does seem clear that three-dimensional effects such as the formation of streamwise ligaments and the pulling back of the sheet at its edges under the action of surface tension are important.

Peck, Bill; Mansour, N. N.; Koga, Dennis (Technical Monitor)

1999-01-01

12

The functional curli amyloid is not based on in-register parallel beta-sheet structure.  

PubMed

The extracellular curli proteins of Enterobacteriaceae form fibrous structures that are involved in biofilm formation and adhesion to host cells. These curli fibrils are considered a functional amyloid because they are not a consequence of misfolding, but they have many of the properties of protein amyloid. We confirm that fibrils formed by CsgA and CsgB, the primary curli proteins of Escherichia coli, possess many of the hallmarks typical of amyloid. Moreover we demonstrate that curli fibrils possess the cross-beta structure that distinguishes protein amyloid. However, solid state NMR experiments indicate that curli structure is not based on an in-register parallel beta-sheet architecture, which is common to many human disease-associated amyloids and the yeast prion amyloids. Solid state NMR and electron microscopy data are consistent with a beta-helix-like structure but are not sufficient to establish such a structure definitively. PMID:19574225

Shewmaker, Frank; McGlinchey, Ryan P; Thurber, Kent R; McPhie, Peter; Dyda, Fred; Tycko, Robert; Wickner, Reed B

2009-09-11

13

Diffraction from the beta-sheet crystallites in spider silk  

E-print Network

We analyze the wide angle x-ray scattering from oriented spider silk fibers in terms of a quantitative scattering model, including both structural and statistical parameters of the $\\beta$-sheet crystallites of spider silk in the amorphous matrix. The model is based on kinematic scattering theory and allows for rather general correlations of the positional and orientational degrees of freedom, including the crystallite's size, composition and dimension of the unit cell. The model is evaluated numerically and compared to experimental scattering intensities allowing us to extract the geometric and statistical parameters. We show explicitly that for the experimentally found mosaicity (width of the orientational distribution) inter-crystallite effects are negligible and the data can be analyzed in terms of single crystallite scattering, as is usually assumed in the literature.

Stephan Ulrich; Anja Glišovi?; Tim Salditt; Annette Zippelius

2008-11-25

14

Learning from nature: beta-sheet-mimicking copolymers get organized.  

PubMed

The solution structures formed by coil-coil copolymers arise from the selective solvation of one of the two blocks and have been well described. In most cases in such relatively simple synthetic structures there are no specific attractive forces that can aid the aggregation process. Nature, however, provides plenty of inspiring polymeric architectures that are shaped and ordered hierarchically by noncovalent forces. The high level of structural definition displayed by proteins, for example, is unmatched by synthetic polymers. An emerging area of interest in polymer science tries to combine the best of both worlds, the natural and the synthetic, by conjugating synthetic polymers and beta-sheet-forming peptides. Understanding the supramolecular organization of the block copolymers driven exclusively by the intermolecular attractive forces of the peptide sequence is of particular interest. Not only do these peptide-polymer hybrid structures present an interesting new class of materials, they can also provide important insights into self-organization processes prevalent in nature. PMID:17912734

König, Hannah M; Kilbinger, Andreas F M

2007-01-01

15

Stability of the beta-sheet of the WW domain: A molecular dynamics simulation study.  

PubMed

The WW domain consists of approximately 40 residues, has no disulfide bridges, and forms a three-stranded antiparallel beta-sheet that is monomeric in solution. It thus provides a model system for studying beta-sheet stability in native proteins. We performed molecular dynamics simulations of two WW domains, YAP65 and FBP28, with very different stability characteristics, in order to explore the initial unfolding of the beta-sheet. The less stable YAP domain is much more sensitive to simulation conditions than the FBP domain. Under standard simulation conditions in water (with or without charge-balancing counterions) at 300 K, the beta-sheet of the YAP WW domain disintegrated at early stages of the simulations. Disintegration commenced with the breakage of a hydrogen bond between the second and third strands of the beta-sheet due to an anticorrelated transition of the Tyr-28 psi and Phe-29 phi angles. Electrostatic interactions play a role in this event, and the YAP WW domain structure is more stable when simulated with a complete explicit model of the surrounding ionic strength. Other factors affecting stability of the beta-sheet are side-chain packing, the conformational entropy of the flexible chain termini, and the binding of cognate peptide. PMID:10512838

Ibragimova, G T; Wade, R C

1999-10-01

16

Stability of the beta-sheet of the WW domain: A molecular dynamics simulation study.  

PubMed Central

The WW domain consists of approximately 40 residues, has no disulfide bridges, and forms a three-stranded antiparallel beta-sheet that is monomeric in solution. It thus provides a model system for studying beta-sheet stability in native proteins. We performed molecular dynamics simulations of two WW domains, YAP65 and FBP28, with very different stability characteristics, in order to explore the initial unfolding of the beta-sheet. The less stable YAP domain is much more sensitive to simulation conditions than the FBP domain. Under standard simulation conditions in water (with or without charge-balancing counterions) at 300 K, the beta-sheet of the YAP WW domain disintegrated at early stages of the simulations. Disintegration commenced with the breakage of a hydrogen bond between the second and third strands of the beta-sheet due to an anticorrelated transition of the Tyr-28 psi and Phe-29 phi angles. Electrostatic interactions play a role in this event, and the YAP WW domain structure is more stable when simulated with a complete explicit model of the surrounding ionic strength. Other factors affecting stability of the beta-sheet are side-chain packing, the conformational entropy of the flexible chain termini, and the binding of cognate peptide. PMID:10512838

Ibragimova, G T; Wade, R C

1999-01-01

17

Numerical simulation of current sheet formation in a quasiseparatrix layer using adaptive mesh refinement  

SciTech Connect

The formation of a thin current sheet in a magnetic quasiseparatrix layer (QSL) is investigated by means of numerical simulation using a simplified ideal, low-{beta}, MHD model. The initial configuration and driving boundary conditions are relevant to phenomena observed in the solar corona and were studied earlier by Aulanier et al. [Astron. Astrophys. 444, 961 (2005)]. In extension to that work, we use the technique of adaptive mesh refinement (AMR) to significantly enhance the local spatial resolution of the current sheet during its formation, which enables us to follow the evolution into a later stage. Our simulations are in good agreement with the results of Aulanier et al. up to the calculated time in that work. In a later phase, we observe a basically unarrested collapse of the sheet to length scales that are more than one order of magnitude smaller than those reported earlier. The current density attains correspondingly larger maximum values within the sheet. During this thinning process, which is finally limited by lack of resolution even in the AMR studies, the current sheet moves upward, following a global expansion of the magnetic structure during the quasistatic evolution. The sheet is locally one-dimensional and the plasma flow in its vicinity, when transformed into a comoving frame, qualitatively resembles a stagnation point flow. In conclusion, our simulations support the idea that extremely high current densities are generated in the vicinities of QSLs as a response to external perturbations, with no sign of saturation.

Effenberger, Frederic [Theoretische Physik IV, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Thust, Kay; Grauer, Rainer; Dreher, Juergen [Theoretische Physik I, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Arnold, Lukas [Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich (Germany)

2011-03-15

18

Thermodynamics of beta-amyloid fibril formation.  

PubMed

Amyloid fibers are aggregates of proteins. They are built out of a peptide called beta-amyloid (Abeta) containing between 41 and 43 residues, produced by the action of an enzyme which cleaves a much larger protein known as the amyloid precursor protein (APP). X-ray diffraction experiments have shown that these fibrils are rich in beta-structures, whereas the shape of the peptide displays an alpha-helix structure within the APP in its biologically active conformation. A realistic model of fibril formation is developed based on the 17 residues Abeta12-28 amyloid peptide, which has been shown to form fibrils structurally similar to those of the whole Abeta peptide. With the help of physical arguments and in keeping with experimental findings, the Abeta12-28 monomer is assumed to be in four possible states (i.e., native helix conformation, beta-hairpin, globular low-energy state, and unfolded state). Making use of these monomeric states, oligomers (dimers, tertramers, and octamers) were constructed. With the help of short, detailed molecular dynamics calculations of the three monomers and of a variety of oligomers, energies for these structures were obtained. Making use of these results within the framework of a simple yet realistic model to describe the entropic terms associated with the variety of amyloid conformations, a phase diagram can be calculated of the whole many-body system, leading to a thermodynamical picture in overall agreement with the experimental findings. In particular, the existence of micellar metastable states seem to be a key issue to determine the thermodynamical properties of the system. PMID:15267752

Tiana, G; Simona, F; Broglia, R A; Colombo, G

2004-05-01

19

Formation of current sheets in magnetic reconnection  

NASA Astrophysics Data System (ADS)

An ideal evolution of magnetic fields in three spatial dimensions tends to cause neighboring field lines to increase their separation exponentially with distance ? along the lines, ? ( ? ) = ? ( 0 ) e ? ( ? ). The non-ideal effects required to break magnetic field line connections scale as e - ?, so the breaking of connections is inevitable for ? sufficiently large—even though the current density need nowhere be large. When the changes in field line connections occur rapidly compared to an Alfvén transit time, the constancy of j | | / B along the magnetic field required for a force-free equilibrium is broken in the region where the change occurs, and an Alfvénic relaxation of j | | / B occurs. Independent of the original spatial distribution of j | | / B, the evolution is into a sheet current, which is stretched by a factor e? in width and contracted by a factor e? in thickness with the current density j | | increasing as e?. The dissipation of these sheet currents and their associated vorticity sheets appears to be the mechanism for transferring energy from a reconnecting magnetic field to a plasma. Harris sheets, which are used in models of magnetic reconnection, are shown to break up in the direction of current flow when they have a finite width and are in a plasma in force equilibrium. The dependence of the longterm nature of magnetic reconnection in systems driven by footpoint motion can be studied in a model that allows qualitative variation in the nature of that motion: slow or fast motion compared to the Alfvén transit time and the neighboring footpoints either exponentially separating in time or not.

Boozer, Allen H.

2014-07-01

20

Multi-layer Parallel Beta-Sheet Structure of Amyloid Beta peptide (1-40) aggregate observed by discrete molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

New evidence shows that oligomeric forms of Amyloid-Beta are potent neurotoxins that play a major role in neurodegeneration of Alzheimer's disease. Detailed knowledge of the structure and assembly dynamics of Amyloid-Beta is important for the development of new therapeutic strategies. Here we apply a two-atom model with Go interactions to model aggregation of Amyloid-Beta (1-40) peptides using the discrete molecular dynamics simulation. At temperatures above the transition temperature from an alpha-helical to random coil, we obtain two types of parallel beta-sheet structures, (a) a helical beta-sheet structure at a lower temperature and (b) a parallel beta-sheet structure at a higher temperature, both with inter-sheet distance of 10 A and with free edges which possibly enable further fibrillar elongation.

Peng, Shouyong; Urbanc, Brigita; Ding, Feng; Cruz, Luis; Buldyrev, Sergey; Dokholyan, Nikolay; Stanley, H. E.

2003-03-01

21

Phase Diagram of alpha-Helical and beta-Sheet Forming Peptides  

E-print Network

The intrinsic property of proteins to form structural motifs such as alpha-helices and beta-sheets leads to a complex phase behavior in which proteins can assemble into various types of aggregates including crystals, liquidlike phases of unfolded or natively folded proteins, and amyloid fibrils. Here we use a coarse-grained protein model that enables us to perform Monte Carlo simulations for determining the phase diagram of natively folded alpha-helical and unfolded beta-sheet forming peptides. The simulations reveal the existence of various metastable peptide phases. The liquidlike phases are metastable with respect to the fibrillar phases, and there is a hierarchy of metastability.

Stefan Auer; Dimo Kashchiev

2010-06-07

22

On spontaneous formation of current sheets: Untwisted magnetic fields  

SciTech Connect

This is a study of the spontaneous formation of electric current sheets in an incompressible viscous fluid with perfect electrical conductivity, governed by the magnetohydrodynamic Navier-Stokes equations. Numerical solutions to two initial value problems are presented for a three-dimensional, periodic, untwisted magnetic field evolving, with no change in magnetic topology under the frozen-in condition and at characteristic fluid Reynolds numbers of the order of 500, from a nonequilibrium initial state with the fluid at rest. The evolution converts magnetic free energy into kinetic energy to be all dissipated away by viscosity so that the field settles into a minimum-energy, static equilibrium. The solutions demonstrate that, as a consequence of the frozen-in condition, current sheets must form during the evolution despite the geometric simplicity of the prescribed initial fields. In addition to the current sheets associated with magnetic neutral points and field reversal layers, other sheets not associated with such magnetic features are also in evidence. These current sheets form on magnetic flux surfaces. This property is used to achieve a high degree of the frozen-in condition in the simulations, by describing the magnetic field entirely in terms of the advection of its flux surfaces and integrating the resulting governing equations with a customized version of a general-purpose high-resolution (viz., nonoscillatory) hydrodynamical simulation code EULAG [J. M. Prusa et al., Comput. Fluids 37, 1193 (2008)]. Incompressibility imposes the additional global constraint that the flux surfaces must evolve with no change in the spatial volumes they enclose. In this approach, current sheet formation is demonstrated graphically by the progressive pressing together of suitably selected flux surfaces until their separation has diminished below the minimal resolved distance on a fixed grid. The frozen-in condition then fails in the simulation as the field reconnects through an effecting numerical resistivity. The principal results are related to the Parker theory of current-sheet formation and dissipation in the solar corona.

Bhattacharyya, R. [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India); National Center for Atmospheric Research, P.O. Box 3000, Boulder, Colorado 80307 (United States); Low, B. C.; Smolarkiewicz, P. K. [National Center for Atmospheric Research, P.O. Box 3000, Boulder, Colorado 80307 (United States)

2010-11-15

23

alpha Helical, but not beta Sheet, Propensity of Proline is Determined by Peptide Environment  

Microsoft Academic Search

Proline is established as a potent breaker of both alpha -helical and beta -sheet structures in soluble (globular) proteins. Thus, the frequent occurrence of the Pro residue in the putative transmembrane helices of integral membrane proteins, particularly transport proteins, presents a structural dilemma. We propose that this phenomenon results from the fact that the structural propensity of a given amino

Shun-Cheng Li; Natalie K. Goto; Karen A. Williams; Charles M. Deber

1996-01-01

24

Designed ?-sheet peptides inhibit amyloid formation by targeting toxic oligomers  

PubMed Central

Previous studies suggest that the toxic soluble-oligomeric form of different amyloid proteins share a common backbone conformation, but the amorphous nature of this oligomer prevents its structural characterization by experiment. Based on molecular dynamics simulations we proposed that toxic intermediates of different amyloid proteins adopt a common, nonstandard secondary structure, called ?-sheet. Here we report the experimental characterization of peptides designed to be complementary to the ?-sheet conformation observed in the simulations. We demonstrate inhibition of aggregation in two different amyloid systems, ?-amyloid peptide (A?) and transthyretin, by these designed ?-sheet peptides. When immobilized the ?-sheet designs preferentially bind species from solutions enriched in the toxic conformer compared with non-aggregated, nontoxic species or mature fibrils. The designs display characteristic spectroscopic signatures distinguishing them from conventional secondary structures, supporting ?-sheet as a structure involved in the toxic oligomer stage of amyloid formation and paving the way for novel therapeutics and diagnostics. DOI: http://dx.doi.org/10.7554/eLife.01681.001 PMID:25027691

Hopping, Gene; Kellock, Jackson; Barnwal, Ravi Pratap; Law, Peter; Bryers, James; Varani, Gabriele; Caughey, Byron; Daggett, Valerie

2014-01-01

25

Thermally Induced Alpha-Helix to Beta-Sheet Transition in Regenerated Silk Fibers and Films  

SciTech Connect

The structure of thin films cast from regenerated solutions of Bombyx mori cocoon silk in hexafluoroisopropyl alcohol (HFIP) was studied by synchrotron X-ray diffraction during heating. A solid-state conformational transition from an alpha-helical structure to the well-known beta-sheet silk II structure occurred at a temperature of approximately 140 degrees C. The transition appeared to be homogeneous, as both phases do not coexist within the resolution of the current study. Modulated differential scanning calorimetry (DSC) of the films showed an endothermic melting peak followed by an exothermic crystallization peak, both occurring near 140 degrees C. Oriented fibers were also produced that displayed this helical molecular conformation. Subsequent heating above the structural transition temperature produced oriented beta-sheet fibers very similar in structure to B. mori cocoon fibers. Heat treatment of silk films at temperatures well below their degradation temperature offers a controllable route to materials with well-defined structures and mechanical behavior.

Drummy,L.; Phillips, D.; Stone, M.; Farmer, B.; Naik, R.

2005-01-01

26

Para, ferro- and antiferro-magnetic order in beta-sheet tapes of oligopeptides  

Microsoft Academic Search

Beta-sheet-forming peptides give rise to self-assembled hierarchical structures such as tapes, ribbons and fibrils, which at sufficiently high concentrations form nematic liquid crystalline solutions and gels. Applications of these novel materials are found in nanotechnology, medicine and personal care products. Such aggregates not only appear in the context of desirable biomaterials but also in pathological self-assembly of mis-folded proteins, forming

Sara Jabbari-Farouji; Paul van der Schoot

2009-01-01

27

Formation of sheeting joints in Yosemite National Park, California  

NASA Astrophysics Data System (ADS)

The formation of sheeting joints (i.e., "exfoliation joints"), opening mode fractures subparallel to the Earth's surface, has been a classic unresolved problem in geology. Diverse new observations and analyses support the hypothesis that sheeting joints develop in response to a near-surface tension induced by compressive stresses parallel to a convex slope (hypothesis 1) rather than the conventional explanation that the joints form as a result of removal of overburden by erosion (hypothesis 2). The opening mode displacements across the joints together with the absence of mineral precipitates within the joints mean that sheeting joints open in response to a near-surface tension normal to the surface (N) rather than a pressurized fluid. An absolute tension must arise in the shallow subsurface if a plot of N as a function of depth normal to the surface (z) has a positive slope at the surface (z=0). The differential equations of static equilibrium require that this slope (derivative) equals k2 P22 + k3 P33 - ?g cosβ, where k2 and k3 are the principal curvatures of the surface, P22 and P33 are the respective surface-parallel normal stresses along the principal curvatures, ? is the material density, g is gravitational acceleration, and β is the slope. This derivative will be positive and sheeting joints can open if the surface-parallel stress in at least one direction is sufficiently compressive (negative) and the curvature in that direction is sufficiently convex (negative). Hypotheses 1 and 2 are being tested using geologic mapping and aerial LIDAR data from Yosemite National Park, California. The abundance of sheeting joints on convex ridges there, where erosion is a local minimum, coupled with their scarcity in the adjacent concave valleys, where erosion is a local maximum, is consistent with hypothesis 1 but inconsistent with hypothesis 2. At several sites with sheeting joints, measurements of the current topographic curvatures and the current surface-parallel stresses, typically about -10 MPa, meet the requirement above. In apparent violation of hypothesis 1, however, sheeting joints occur locally at the bottom of Tenaya Canyon, one of the park's deepest glaciated, U-shaped (concave) canyons in Yosemite. The sheeting joints occur only where the canyon is convex in the downstream direction though, and that is the approximate direction of the most compressive stress based on nearby stress measurements. Apparently the effect of the least compressive stress acting across the valley, which acts to close the joints, is overcome by the effect of the most compressive stress acting along the down-valley convex curvature, which promotes the opening of the joints.

Martel, S. J.

2009-04-01

28

CURRENT SHEETS FORMATION IN TANGLED CORONAL MAGNETIC FIELDS  

SciTech Connect

We investigate the dynamical evolution of magnetic fields in closed regions of solar and stellar coronae. To understand under which conditions current sheets form, we examine dissipative and ideal reduced magnetohydrodynamic models in Cartesian geometry, where two magnetic field components are present: the strong guide field B{sub 0}, extended along the axial direction, and the dynamical orthogonal field b. Magnetic field lines thread the system along the axial direction that spans the length L and are line-tied at the top and bottom plates. The magnetic field b initially has only large scales, with its gradient (current) length scale of the order of l{sub b}. We identify the magnetic intensity threshold b/B{sub 0} {approx} l{sub b}/L. For values of b below this threshold, field-line tension inhibits the formation of current sheets, while above the threshold they form quickly on fast ideal timescales. In the ideal case, above the magnetic threshold, we show that current sheets thickness decreases in time until it becomes smaller than the grid resolution, with the analyticity strip width {delta} decreasing at least exponentially, after which the simulations become underresolved.

Rappazzo, A. F. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Parker, E. N., E-mail: franco.rappazzo@gmail.com, E-mail: parker@oddjob.uchicago.edu [Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States)

2013-08-10

29

Effect of beta-sheet crystals on the thermal and rheological behavior of protein-based hydrogels derived from gelatin and silk fibroin.  

PubMed

Novel protein-based hydrogels have been prepared by blending gelatin (G) with amorphous Bombyx mori silk fibroin (SF) and subsequently promoting the formation of beta-sheet crystals in SF upon exposure to methanol or methanol/water solutions. Differential scanning calorimetry of the resultant hydrogels confirms the presence and thermoreversibility of the G helix-coil transition between ambient and body temperature at high G concentrations. At low G concentrations, this transition is shifted to higher temperatures and becomes progressively less pronounced. Complementary dynamic rheological measurements reveal solid-liquid cross-over at the G helix-coil transition temperature typically between 30 and 36 degrees C in blends prior to the formation of beta-sheet crystals. Introducing the beta-sheet conformation in SF stabilizes the hydrogel network and extends the solid-like behavior of the hydrogels to elevated temperatures beyond body temperature with as little as 10 wt.-% SF. The temperature-dependent elastic modulus across the G helix-coil transition is reversible, indicating that the conformational change in G can be used in stabilized G/SF hydrogels to induce thermally triggered encapsulant release. PMID:16080165

Gil, Eun S; Spontak, Richard J; Hudson, Samuel M

2005-08-12

30

Reversible hydrogel-solution system of silk with high beta-sheet content.  

PubMed

Silkworm silk has been widely used as a textile fiber, as biomaterials and in optically functional materials due to its extraordinary properties. The ?-sheet-rich natural nanofiber units of about 10-50 nm in diameter are often considered the origin of these properties, yet it remains unclear how silk self-assembles into these hierarchical structures. A new system composed of ?-sheet-rich silk nanofibers about 10-20 nm in diameter is reported here, where these nanofibers formed into "flowing hydrogels" at 0.5-2% solutions and could be transformed back into the solution state at lower concentrations, even with a high ?-sheet content. This is in contrast with other silk processed materials, where significant ?-sheet content negates reversibility between solution and solid states. These fibers are formed by regulating the self-assembly process of silk in aqueous solution, which changes the distribution of negative charges while still supporting ?-sheet formation in the structures. Mechanistically, there appears to be a shift toward negative charges along the outside of the silk nanofibers in our present study, resulting in a higher zeta potential (above -50 mV) than previous silk materials which tend to be below -30 mV. The higher negative charge on silk nanofibers resulted in electrostatic repulsion strong enough to negate further assembly of the nanofibers. Changing silk concentration changed the balance between hydrophobic interactions and electrostatic repulsion of ?-sheet-rich silk nanofibers, resulting in reversible hydrogel-solution transitions. Furthermore, the silk nanofibers could be disassembled into shorter fibers and even nanoparticles upon ultrasonic treatment following the transition from hydrogel to solution due to the increased dispersion of hydrophobic smaller particles, without the loss of ?-sheet content, and with retention of the ability to transition between hydrogel and solution states through reversion to longer nanofibers during self-assembly. These reversible solution-hydrogel transitions were tunable with ultrasonic intensity, time, or temperature. PMID:25056606

Bai, Shumeng; Zhang, Xiuli; Lu, Qiang; Sheng, Weiqin; Liu, Lijie; Dong, Boju; Kaplan, David L; Zhu, Hesun

2014-08-11

31

Microphase Separation Controlled beta-Sheet Crystallization Kinetics in Fibrous Proteins  

SciTech Connect

Silk is a naturally occurring fibrous protein with a multiblock chain architecture. As such, it has many similarities with synthetic block copolymers, including the possibility for e-sheet crystallization restricted within the crystallizable blocks. The mechanism of isothermal crystallization kinetics of e-sheet crystals in silk multiblock fibrous proteins is reported in this study. Kinetics theories, such as Avrami analysis which was established for studies of synthetic polymer crystal growth, are for the first time extended to investigate protein self-assembly in e-sheet rich Bombyx mori silk fibroin samples, using time-resolved Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and synchrotron real-time wide-angle X-ray scattering (WAXS). The Avrami exponent, n, was close to 2 for all methods and crystallization temperatures, indicating formation of e-sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in synthetic polymers. Observations by scanning electron microscopy support the view that the protein structures vary during the different stages of crystal growth, and show a microphase separation pattern after chymotrypsin enzyme biodegradation. We present a model to explain the crystallization of the multiblock silk fibroin protein, by analogy to block copolymers: crystallization of e-sheets occurs under conditions of geometrical restriction caused by phase separation of the crystallizable and uncrystallizable blocks. This crystallization model could be widely applicable in other proteins with multiblock (i.e., crystallizable and noncrystallizable) domains.

Hu, X.; Lu, Q; Kaplan, D; Cebe, P

2009-01-01

32

Computer-Based Redesign of a Beta Sandwich Protein Suggests That Extensive Negative Design is not Required for de novo beta Sheet Design  

SciTech Connect

The de novo design of globular {Beta} sheet proteins remains largely an unsolved problem. It is unclear whether most designs are failing because the designed sequences do not have favorable energies in the target conformations or whether more emphasis should be placed on negative design, that is, explicitly identifying sequences that have poor energies when adopting undesired conformations. We tested whether we could redesign the sequence of a naturally occurring {Beta} sheet protein, tenascin, with a design algorithm that does not include explicit negative design. Denaturation experiments indicate that the designs are significantly more stable than the wild-type protein and the crystal structure of one design closely matches the design model. These results suggest that extensive negative design is not required to create well-folded {Beta} sandwich proteins. However, it is important to note that negative design elements may be encoded in the conformation of the protein backbone which was preserved from the wild-type protein.

Hu, X.; Wang, H; Ke, H; Kuhlman, B

2008-01-01

33

Formation of active monomers from tetrameric human beta-tryptase.  

PubMed Central

Tryptase is a serine protease that is stored at low pH in the mast cell secretory granules in complex with heparin proteoglycan. When mast cells are activated, e.g. during allergic responses, the tryptase/heparin complexes are released together with a variety of other preformed inflammatory mediators. Previous crystallization of human beta-tryptase revealed a unique tetrameric structure with all of the active sites facing a central pore that has a limited accessibility both for potential substrates as well as for protease inhibitors. In this study we examined whether human beta-tryptase, in addition, could form active monomers. Incubation of recombinant tetrameric human beta-tryptase at neutral pH and 37 degrees C, followed by gel-filtration analysis using a running buffer containing pig mucosal heparin, led to the formation of enzymically active compounds that were of a size compatible with tryptase monomers in complex with heparin. The monomers were, in contrast to tryptase in the tetrameric form, inhibited by bovine pancreatic trypsin inhibitor. Further, the monomers, but not the tetramers, degraded fibronectin. Formation of active monomers was more pronounced at pH 7.5 than at pH 6.0 and was not detected at room temperature or at high heparin/tryptase ratios. The present findings thus introduce the possibility that human beta-tryptase, after mast cell degranulation and exposure to neutral pH in the tissue, may dissociate into active monomers with properties that are distinct from the tetrameric counterpart. Possibly, some of the biological activities of human tryptase may be attributable to active tryptase in its monomeric rather than tetrameric form. PMID:12387726

Fajardo, Ignacio; Pejler, Gunnar

2003-01-01

34

Involvement of disulfide bonds and histidine 172 in a unique beta-sheet to alpha-helix transition of alpha 1-acid glycoprotein at the biomembrane interface.  

PubMed

Human alpha(1)-acid glycoprotein (AGP), which is comprised of 183 amino acid residues and 5 carbohydrate chains, is a major plasma protein that binds to basic and neutral drugs as well as to steroid hormones. It has a beta-sheet-rich structure in aqueous solution. Our previous findings suggest that AGP forms an alpha-helix structure through an interaction with biomembranes. We report herein on a study of the mechanism of alpha-helix formation in AGP using various modified AGPs. The disulfide reduced AGP (R-AGP) was extensively unfolded, whereas asialylated AGP (A-AGP) maintained the native structure. Intriguingly, reduced and asialylated AGP (RA-AGP) increased the alpha-helix content as observed in the presence of biomembrane models, and showed a significant decrease in ligand binding capacity. This suggests that AGP has an innate tendency to form an alpha-helix structure, and disulfide bonds are a key factor in the conformational transition between the beta-sheet and alpha-helix structures. However, RA-AGP with all histidine residues chemically modified (HRA-AGP) was found to lose the intrinsic ability to form an alpha-helix structure. Furthermore, disulfide reduction of the H172A mutant expressed in Pichia pastoris also caused a similar loss of folding ability. The present results indicate that disulfide bonds and the C-terminal region, including H172 of AGP, play important roles in alpha-helix formation in the interaction of the protein with biomembranes. PMID:16470806

Nishi, Koji; Komine, Yoshio; Fukunaga, Naoko; Maruyama, Toru; Suenaga, Ayaka; Otagiri, Masaki

2006-05-15

35

Plasma-beta dependence of the fast reconnection mechanism in an initially force-free current sheet  

SciTech Connect

The present paper systematically studies the spontaneous fast reconnection mechanism in an initially force-free current sheet in a wide range of plasma beta ({beta}); in our previous work it was studied for a special case of {beta} = 0.15. In each case, the evolution as well as the resulting structure of the fast reconnection is qualitatively similar to the one that was already reported for the case of {beta} = 0.15. Quantitatively, the fast reconnection evolution becomes more rapid and drastic for the lower plasma beta. For the cases of very low plasma beta ({beta} = 0.01 or 0.02), the plasma temperature is extremely enhanced to the value almost 1/{beta} times larger than its initial value in the resulting fast reconnection jet and large-scale plasmoid regions. Once the fast reconnection mechanism is ignited in a local spot-like region, its basic structure eventually established is sustained almost steadily, giving rise to the plasmoid swelling with time and propagating outwards. Accordingly, the characteristic reconnection regions, where plasma thermodynamic quantities are remarkably enhanced, rapidly expand in all (x, y, and z) directions in Alfven time scales, which may be responsible for the explosive expansion of large flares as well as for the distinct plasma heating observed in the solar corona.

Ugai, M. [Research Center for Space and Cosmic Evolution, Ehime University, Matsuyama 790-8577 (Japan)

2011-10-15

36

PB1-F2 influenza A virus protein adopts a beta-sheet conformation and forms amyloid fibers in membrane environments.  

PubMed

The influenza A virus PB1-F2 protein, encoded by an alternative reading frame in the PB1 polymerase gene, displays a high sequence polymorphism and is reported to contribute to viral pathogenesis in a sequence-specific manner. To gain insights into the functions of PB1-F2, the molecular structure of several PB1-F2 variants produced in Escherichia coli was investigated in different environments. Circular dichroism spectroscopy shows that all variants have a random coil secondary structure in aqueous solution. When incubated in trifluoroethanol polar solvent, all PB1-F2 variants adopt an alpha-helix-rich structure, whereas incubated in acetonitrile, a solvent of medium polarity mimicking the membrane environment, they display beta-sheet secondary structures. Incubated with asolectin liposomes and SDS micelles, PB1-F2 variants also acquire a beta-sheet structure. Dynamic light scattering revealed that the presence of beta-sheets is correlated with an oligomerization/aggregation of PB1-F2. Electron microscopy showed that PB1-F2 forms amorphous aggregates in acetonitrile. In contrast, at low concentrations of SDS, PB1-F2 variants exhibited various abilities to form fibers that were evidenced as amyloid fibers in a thioflavin T assay. Using a recombinant virus and its PB1-F2 knock-out mutant, we show that PB1-F2 also forms amyloid structures in infected cells. Functional membrane permeabilization assays revealed that the PB1-F2 variants can perforate membranes at nanomolar concentrations but with activities found to be sequence-dependent and not obviously correlated with their differential ability to form amyloid fibers. All of these observations suggest that PB1-F2 could be involved in physiological processes through different pathways, permeabilization of cellular membranes, and amyloid fiber formation. PMID:20172856

Chevalier, Christophe; Al Bazzal, Ali; Vidic, Jasmina; Février, Vincent; Bourdieu, Christiane; Bouguyon, Edwige; Le Goffic, Ronan; Vautherot, Jean-François; Bernard, Julie; Moudjou, Mohammed; Noinville, Sylvie; Chich, Jean-François; Da Costa, Bruno; Rezaei, Human; Delmas, Bernard

2010-04-23

37

Supramolecular structure in full-length Alzheimer's beta-amyloid fibrils: evidence for a parallel beta-sheet organization from solid-state nuclear magnetic resonance.  

PubMed Central

We report constraints on the supramolecular structure of amyloid fibrils formed by the 40-residue beta-amyloid peptide associated with Alzheimer's disease (A beta(1-40)) obtained from solid-state nuclear magnetic resonance (NMR) measurements of intermolecular dipole-dipole couplings between (13)C labels at 11 carbon sites in residues 2 through 39. The measurements are carried out under magic-angle spinning conditions, using the constant-time finite-pulse radiofrequency-driven recoupling (fpRFDR-CT) technique. We also present one-dimensional (13)C magic-angle spinning NMR spectra of the labeled A beta(1-40) samples. The fpRFDR-CT data reveal nearest-neighbor intermolecular distances of 4.8 +/- 0.5 A for carbon sites from residues 12 through 39, indicating a parallel alignment of neighboring peptide chains in the predominantly beta-sheet structure of the amyloid fibrils. The one-dimensional NMR spectra indicate structural order at these sites. The fpRFDR-CT data and NMR spectra also indicate structural disorder in the N-terminal segment of A beta(1-40), including the first nine residues. These results place strong constraints on any molecular-level structural model for full-length beta-amyloid fibrils. PMID:12124300

Balbach, John J; Petkova, Aneta T; Oyler, Nathan A; Antzutkin, Oleg N; Gordon, David J; Meredith, Stephen C; Tycko, Robert

2002-01-01

38

Formation of structured current sheet in the near-Earth magnetotail  

NASA Astrophysics Data System (ADS)

The current sheet in the magnetotail is a key region for dynamic magnetospheric processes that can cause substorms. Recent multi-point THEMIS observations have clearly displayed that the current sheet in the tail plasma sheet exhibits various structures and evolutions. We study the plasma sheet and the current sheet evolutions as a result of energy input from the solar wind by means of a simple theoretical model, 3D global MHD simulation, and spacecraft observations. Our simple theoretical model and arguments suggest that the tail evolution is determined not only by the solar wind condition but also by the initial plasma sheet structure, namely a degree of stretching of the magnetic geometry, meaning that the radial dependence is important. It can be explained that a bifurcated current sheet is a natural consequence of radial dependence. The 3D global MHD simulation has reproduced similar but more complicated feature of the current sheet during the tail thinning. For example, enhanced field-aligned current is also seen owing to the enhanced lateral field in the compressed plasma sheet. The structured current sheets have been reproduced in the simulation and a partial aspect can be explained by the stretched configuration of the tail, while it is found that the formation processes and origin are not always the same as observations.

Saito, M. H.; Fujita, S.; Seki, K.; Nagai, T.; Ogino, T.

2013-12-01

39

Current Sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-frequency Assisted Discharge  

NASA Technical Reports Server (NTRS)

Data from an inductive conical theta pinch accelerator are presented to gain insight into the process of inductive current sheet formation in the presence of a preionized background gas produced by a steady-state RF-discharge. The presence of a preionized plasma has been previously shown to allow for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts, leading to greater accelerator efficiencies at lower power levels. Time-resolved magnetic probe measurements are obtained for different background pressures and pulse energies to characterize the effects of these parameters on current sheet formation. Indices are defined that describe time-resolved current sheet characteristics, such as the total current owing in the current sheet, the time-integrated total current ('strength'), and current sheet velocity. It is found that for a given electric field strength, maximums in total current, strength, and velocity occur for one particular background pressure. At other pressures, these current sheet indices are considerably smaller. The trends observed in these indices are explained in terms of the principles behind Townsend breakdown that lead to a dependence on the ratio of the electric field to the background pressure. Time-integrated photographic data are also obtained at the same experimental conditions, and qualitatively they compare quite favorably with the time-resolved magnetic field data.

Polzin, Kurt A.; Hallock, Ashley K.; Choueiri, Edgar Y.

2008-01-01

40

The peculiarities of formation of thin current sheet in the Earth's magnetotail  

NASA Astrophysics Data System (ADS)

We investigate the process of self-consistent thinning of magnetotail current sheet in the presence of the evolving magnetic field normal component Bz, which usually decreases during the substorm growth phase. Using PIC codes to describe plasma processes with ions becoming demagnetized and electrons being considered as the cold neutralizing background, we show that the appearance of the self-consistent electric field component inside CS can lead to the current sheet thinning and to the appearance of an extremely thin current sheet with thickness close to the ion gyroradius. Due to particle [ExB] drift during the current sheet evolution, the enhanced trapping of ions near the current sheet central plane takes place. It is shown that the density of quasi-trapped particles around current sheet at the final stage depends on both the value of the initial magnetic field normal component Bz, and the speed of the Bz decrease. If the initial magnetic field normal component is less than about 0.14 of the tangential field at the edges, the trapped plasma density near the current sheet is small. As a result, the above mentioned extremely thin current sheet is formed. In the opposite case, when the initial normal component related to the tangential field is larger than 0.14, the density of trapped particles is much higher, which produces effective thickening of the current sheet. In both cases transient (Speiser) ions are the main current carriers, but in the second case local diamagnetic currents of the trapped plasma perturb the ?urrent sheet profile making it thicker. Also trapped particles can be responsible for intense negative currents at the current sheet edges. During the Bz decrease, an additional effect of ion polarization drifts in the Y direction can compete with these negative diamagnetic fields of quasi-trapped ions. Therefore the ion dynamics is probably the general mechanism which contributes to the formation of thin current sheet and its fine structure.

Kropotkin, Alexey; Artemyev, Anton; Malova, Helmi; Domrin, Vladimir

41

Relating thin current sheet formation and tail reconnection to substorm development  

SciTech Connect

Observations and simulations have demonstrated the important role of thin current sheet formation and magnetic reconnection in the course of substorms. We discuss new results on the formation of thin current sheets, obtained both within MHD and kinetic theory. They demonstrate when kinetic effects become important and indicate the possibility of a catastrophic onset of substorm dynamics and the potential association with arc brightening. MHD simulations show the role of reconnection in the buildup of the substorm current wedge and the influence of the underlying configuration on the quasi-static and dynamic evolution.

Birn, J. (Joachim); Schindler, K.

2002-01-01

42

The formation of wrinkles in single-layer graphene sheets under nanoindentation.  

PubMed

We investigate the formation of wrinkles and bulging in single-layer graphene sheets using an equivalent atomistic continuum nonlinear hyperelastic theory for nanoindentation and nanopressurization. We show that nonlinear geometrical effects play a key role in the development of wrinkles. Without abandoning the classical tension field membrane theory, we develop an enhanced model based upon the minimization of a relaxed energy functional in conjunction with nonlinear finite hyperelasticity. Formation of wrinkles are observed in rectangular graphene sheets due to the combination of induced membrane tension and edge effects under external pressure. PMID:21389525

Gil, A J; Adhikari, S; Scarpa, F; Bonet, J

2010-04-14

43

The formation of wrinkles in single-layer graphene sheets under nanoindentation  

NASA Astrophysics Data System (ADS)

We investigate the formation of wrinkles and bulging in single-layer graphene sheets using an equivalent atomistic continuum nonlinear hyperelastic theory for nanoindentation and nanopressurization. We show that nonlinear geometrical effects play a key role in the development of wrinkles. Without abandoning the classical tension field membrane theory, we develop an enhanced model based upon the minimization of a relaxed energy functional in conjunction with nonlinear finite hyperelasticity. Formation of wrinkles are observed in rectangular graphene sheets due to the combination of induced membrane tension and edge effects under external pressure.

Gil, A. J.; Adhikari, S.; Scarpa, F.; Bonet, J.

2010-04-01

44

Numerical simulation of current sheet formation in a quasiseparatrix layer using adaptive mesh refinement  

NASA Astrophysics Data System (ADS)

The formation of a thin current sheet in a magnetic quasiseparatrix layer (QSL) is investigated by means of numerical simulation using a simplified ideal, low-?, MHD model. The initial configuration and driving boundary conditions are relevant to phenomena observed in the solar corona and were studied earlier by Aulanier et al. [Astron. Astrophys. 444, 961 (2005)]. In extension to that work, we use the technique of adaptive mesh refinement (AMR) to significantly enhance the local spatial resolution of the current sheet during its formation, which enables us to follow the evolution into a later stage. Our simulations are in good agreement with the results of Aulanier et al. up to the calculated time in that work. In a later phase, we observe a basically unarrested collapse of the sheet to length scales that are more than one order of magnitude smaller than those reported earlier. The current density attains correspondingly larger maximum values within the sheet. During this thinning process, which is finally limited by lack of resolution even in the AMR studies, the current sheet moves upward, following a global expansion of the magnetic structure during the quasistatic evolution. The sheet is locally one-dimensional and the plasma flow in its vicinity, when transformed into a comoving frame, qualitatively resembles a stagnation point flow. In conclusion, our simulations support the idea that extremely high current densities are generated in the vicinities of QSLs as a response to external perturbations, with no sign of saturation.

Effenberger, Frederic; Thust, Kay; Arnold, Lukas; Grauer, Rainer; Dreher, Jürgen

2011-03-01

45

A globular protein with slower amide proton exchange from an alpha helix than from antiparallel beta sheets.  

PubMed

In proteinase inhibitor IIA from bull seminal plasma, which is a small globular protein with 57 amino acid residues, measurements of individual amide proton exchange rates by two-dimensional correlated 1H NMR spectroscopy (COSY) showed that the exchange was slowest for some hydrogen bonded amide groups in an alpha-helix. This contrasts with all other proteins which were so far studied in detail, where the slowest exchange rates were observed for hydrogen bonded amide protons in antiparallel beta-sheets. PMID:6477556

Wüthrich, K; Strop, P; Ebina, S; Williamson, M P

1984-08-16

46

Non-Equilibrium and Current Sheet Formation in Line-Tied  

E-print Network

· A theorem on Parker's model [Ng & Bhattacharjee, 1998] · Future directions Solar corona: heating problem://science.nasa.gov/ssl/PAD/solar/quests.htm Solar corona: heating problem #12;Solar corona: basic parameters photosphere corona Temperature DensityNon-Equilibrium and Current Sheet Formation in Line-Tied Magnetic Fields: Heating of the Solar

Ng, Chung-Sang

47

Effect of temperature on texture formation of 6061 aluminum sheet in equal-channel angular pressing  

Microsoft Academic Search

A novel equal-channel angular pressing (ECAP) procedure was conducted on 6061 aluminum sheet at temperature up to 513K to investigate temperature effect on microstructure and texture formation. The deformed microstructures were examined by transmission electron microscopy and the macrotexture evolution was investigated by orientation distribution functions (ODFs). The results shown that when ECAP at temperature below 433K the microstructures exhibit

Qin Jining; Zhang Di; Zhang Guoding; Jae-Chul Lee

2005-01-01

48

The formation of wrinkles in single-layer graphene sheets under nanoindentation  

Microsoft Academic Search

We investigate the formation of wrinkles and bulging in single-layer graphene sheets using an equivalent atomistic continuum nonlinear hyperelastic theory for nanoindentation and nanopressurization. We show that nonlinear geometrical effects play a key role in the development of wrinkles. Without abandoning the classical tension field membrane theory, we develop an enhanced model based upon the minimization of a relaxed energy

A. J. Gil; S. Adhikari; F. Scarpa; J. Bonet

2010-01-01

49

Bond formation in ultrasonically welded aluminum sheet metal  

NASA Astrophysics Data System (ADS)

Ultrasonic welding (USW), a solid state joining technology, has been used to bond aluminum alloys commonly used in the automotive industry. Bonding occurs due to USW's high frequency (˜20 kHz) in-plane vibration of sample interfaces while being held under moderate clamp pressure normal to the plane of vibration. Vibration and clamp pressure are transmitted into bond formation via contact with a weld-tip. To better understand how weld-tip geometry affected bond formation, experiments were conducted to quantify how tip geometry influenced plastic deformation characteristics between fully welded coupons of 0.9mm thick AA6111-T4 aluminum alloy. Weld-interface microstructure features were documented by optical microscopy and features quantified in a 19 point matrix. Correlation between microstructure features, such as rolling-wakes, and resulting weld bond strengths of more than 3.0kN is made. Weld zone microstructure features appear to result from deformation at and severe migration of the original weld interface during USW. To confirm this hypothesis, intrinsic and extrinsic markers were employed to monitor weld interface deformation characteristics. Various physical and analytical techniques were used in conjunction with these markers to show that joining of "like" and "dislike" aluminum samples is achieved through mechanical mixing of mating interfaces and not by elemental diffusion. It is also hypothesized that severe deformation of the original interface would result in areas of high residual strain within a formed weld zone. To investigate this and the influence that tip geometry may have on residual strain, fully welded samples were annealed at 500°C for a controlled period of time and recovery, recrystallization and grain growth characteristics were monitored. In all welds, initial recrystallization and grain growth occurred at the outer ends of weld zones and along weld interfaces where the most turbulent mixing and grain size reduction was observed. Similarity in how all welds responded to annealing indicates that the tip geometries investigated had little influence on resulting weld formation. This claim is further supported by lap-shear failure load data for welds made with these tips being within statistical error of each other.

Wilkosz, Daniel Edward

50

Entrainment of prefrontal beta oscillations induces an endogenous echo and impairs memory formation.  

PubMed

Brain oscillations across all frequency bands play a key role for memory formation. Specifically, desynchronization of local neuronal assemblies in the left inferior prefrontal cortex (PFC) in the beta frequency (?18 Hz) has been shown to be central for encoding of verbal memories. However, it remains elusive whether prefrontal beta desynchronization is causally relevant for memory formation and whether these endogenous beta oscillations can be entrained by external stimulation. By using combined EEG-TMS (transcranial magnetic stimulation), we here address these fundamental questions in human participants performing a word-list learning task. Confirming our predictions, memory encoding was selectively impaired when the left inferior frontal gyrus (IFG) was driven at beta (18.7 Hz) compared to stimulation at other frequencies (6.8 Hz and 10.7 Hz) and to ineffective sham stimulation (18.7 Hz). Furthermore, a sustained oscillatory "echo" in the left IFG, which outlasted the stimulation period by approximately 1.5 s, was observed solely after beta stimulation. The strength of this beta echo was related to memory impairment on a between-subjects level. These results show endogenous oscillatory entrainment effects and behavioral impairment selectively in beta frequency for stimulation of the left IFG, demonstrating an intimate causal relationship between prefrontal beta desynchronization and memory formation. PMID:24684933

Hanslmayr, Simon; Matuschek, Jonas; Fellner, Marie-Christin

2014-04-14

51

Phi-analysis at the experimental limits: mechanism of beta-hairpin formation.  

PubMed

The 37-residue Formin-binding protein, FBP28, is a canonical three-stranded beta-sheet WW domain. Because of its small size, it is so insensitive to chemical denaturation that it is barely possible to determine accurately a denaturation curve, as the transition spans 0-7 M guanidinium hydrochloride (GdmCl). It is also only marginally stable, with a free energy of denaturation of just 2.3 kcal/mol at 10 degrees Celsius so only small changes in energy upon mutation can be tolerated. But these properties and relaxation times for folding of 25 micros-400 micros conspire to allow the rapid acquisition of accurate and reproducible kinetic data for Phi-analysis using classical temperature-jump methods. The transition state for folding is highly polarized with some regions having Phi-values of 0 and others 1, as readily seen in chevron plots, with Phi-values of 0 having the refolding arms overlaying and those of 1 the unfolding arms superimposable. Good agreement is seen with transition state structures identified from independent molecular dynamics (MD) simulations at 60, 75, and 100 degrees Celsius, which allows us to explore further the details of the folding and unfolding pathway of FBP28. The first beta-turn is near native-like in the transition state for folding (experimental) and unfolding (MD and experiment). The simulations show that there are transient contacts between the aromatic side-chains of the beta-strands in the denatured state and that these interactions provide the driving force for folding of the first beta-hairpin of this three-stranded sheet. Only after the backbone hydrogen bonds are formed between beta1 and beta2 does a hydrogen bond form to stabilize the intervening turn, or the first beta-turn. PMID:16784750

Petrovich, Miriana; Jonsson, Amanda L; Ferguson, Neil; Daggett, Valerie; Fersht, Alan R

2006-07-21

52

Nature of axial tail instability and bubble-blob formation in near-Earth plasma sheet  

NASA Astrophysics Data System (ADS)

revious global magnetohydrodynamic (MHD) simulations of substorm events have identified the dynamic presence of an axial tail instability that is uniform in the dawn-dusk direction in the near-Earth plasma sheet. The axial tail instability is found to be a major cause of the initial growing MHD force imbalance on closed field lines prior to the subsequent magnetic reconnection and substorm expansion onset processes. In this work, energy principle analysis indicates that a two-dimensional thin current sheet configuration in the magnetotail is typically stable to the axial mode within the framework of ideal MHD model. However, linear resistive MHD calculations find axial tail instabilities on closed field lines in the generalized Harris sheet configurations. The properties of these instabilities are similar to the axial tail modes observed in the global MHD simulations. The axial tail mode is unstable in regimes of low Lundquist number and regions with small normal component of magnetic field. Such resistive axial tail instability would by many researchers be considered as tearing instability in a two-dimensional tail configuration. Unlike the conventional tearing mode of Harris sheet, the linear axial tail instability does not involve any reconnection process. Instead, the nature of the mode is dominantly a slippage process among neighboring flux tubes as facilitated by resistive dissipation. A natural consequence of the axial tail instability is shown to be the formation of bubble-blob pairs in the pressure and entropy profiles in the near-Earth plasma sheet.

Zhu, P.; Raeder, J.; Hegna, C. C.; Sovinec, C. R.

2013-02-01

53

FORMATION AND RECONNECTION OF THREE-DIMENSIONAL CURRENT SHEETS IN THE SOLAR CORONA  

SciTech Connect

Current-sheet formation and magnetic reconnection are believed to be the basic physical processes responsible for much of the activity observed in astrophysical plasmas, such as the Sun's corona. We investigate these processes for a magnetic configuration consisting of a uniform background field and an embedded line dipole, a topology that is expected to be ubiquitous in the corona. This magnetic system is driven by a uniform horizontal flow applied at the line-tied photosphere. Although both the initial field and the driver are translationally symmetric, the resulting evolution is calculated using a fully three-dimensional (3D) magnetohydrodynamic simulation with adaptive mesh refinement that resolves the current sheet and reconnection dynamics in detail. The advantage of our approach is that it allows us to directly apply the vast body of knowledge gained from the many studies of two-dimensional (2D) reconnection to the fully 3D case. We find that a current sheet forms in close analogy to the classic Syrovatskii 2D mechanism, but the resulting evolution is different than expected. The current sheet is globally stable, showing no evidence for a disruption or a secondary instability even for aspect ratios as high as 80:1. The global evolution generally follows the standard Sweet-Parker 2D reconnection model except for an accelerated reconnection rate at a very thin current sheet, due to the tearing instability and the formation of magnetic islands. An interesting conclusion is that despite the formation of fully 3D structures at small scales, the system remains close to 2D at global scales. We discuss the implications of our results for observations of the solar corona.

Edmondson, J. K. [NASA Jet Propulsion Laboratory, Pasadena, CA 91109 (United States); Antiochos, S. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); DeVore, C. R. [Naval Research Laboratory, Washington, DC 20375 (United States); Zurbuchen, T. H., E-mail: jkedmond@umich.ed [Department of Atmospheric, Oceanic, and Space Science, University of Michigan, Ann Arbor, MI 48105 (United States)

2010-07-20

54

A Molecular Model of Alzheimer Amyloid beta Peptide Fibril Formation  

Microsoft Academic Search

Polymerization of the amyloid beta (Ab) peptide into protease-resistant fibrils is a significant step in the pathogenesis of Alzheimer's disease. It has not been pos- sible to obtain detailed structural information about this process with conventional techniques because the peptide has limited solubility and does not form crys- tals. In this work, we present experimental results lead- ing to a

Lars O. Tjernberg; David J. E. Callaway; Agneta Tjernbergi; Solveig Hahne; Christina Lilliehook; Lars Terenius; Johan Thyberg; Christer Nordstedt

1999-01-01

55

Swelling and folding as mechanisms of 3D shape formation in thin elastic sheets  

NASA Astrophysics Data System (ADS)

We work with two different mechanisms to generate geometric frustration on thin elastic sheets; isotropic differential growth and folding. We describe how controlled growth and prescribing folding patterns are useful tools for designing three-dimensional objects from information printed in two dimensions. The first mechanism is inspired by the possibility to control shapes by swelling polymer films, where we propose a solution for the problem of shape formation by asking the question, “what 2D metric should be prescribed to achieve a given 3D shape?”', namely the reverse problem. We choose two different types of initial configurations of sheets, disk-like with one boundary and annular with two boundaries. We demonstrate our technique by choosing four examples of 3D axisymmetric shapes and finding the respective swelling factors to achieve the desired shape. Second, we present a mechanical model for a single curved fold that explains both the buckled shape of a closed fold and its mechanical stiffness. The buckling arises from the geometrical frustration between the prescribed crease angle and the bending energy of the sheet away from the crease. This frustration increases as the sheet's area increases. Stiff folds result in creases with constant space curvature while softer folds inherit the broken symmetry of the buckled shape. We extend the application of our numerical model to show the potential to study multiple fold structures.

Dias, Marcelo A.

56

Landscape formation by past continental ice sheets: insights into the subglacial environment  

NASA Astrophysics Data System (ADS)

Glaciers and ice sheets are known as most powerful, climatically driven agents of large-scale sediment redistribution and landscape formation in the Earth system. During the Quaternary, repeated waxing and waning of continental ice sheets contributed to profound reshaping of the Earth surface and set the scene for the development of ecosystems in the post-glacial time. Despite the well-established impact of glaciers on the upper lithosphere the specific processes of glacial erosion, transport and deposition and the formation landforms at the ice-bed interface are contentious. In particular, the relative importance of direct ice impact versus the impact of glacial meltwater is highly controversial. Here, we focus on the southern peripheral area of the Scandinavian Ice Sheet hosting thick successions of soft, deformable sediments and examine some spectacular sediment/landform assemblages found nowadays in both terrestrial and marine settings to illustrate the nature of the subglacial processes. In order to decipher the past ice sheet behavior field, experimental and numerical approaches are combined. It is shown that the strength of the coupling between the ice and the bed that controls the response of the substratum to ice overriding and stress propagation depends primarily on the ability of the glacial system to evacuate meltwater from ice-bed interface. Strong coupling, locally enhanced by subglacial permafrost resulted in deeply rooted (100's of meters) glaciotectonic deformation reflected on the surface as ice-shoved hills whereas weak coupling promoted by water accumulating under the ice triggered the formation of deep (100's of meters) tunnel valley networks. Under the arteries of fast-flowing ice known as palaeo-ice streams, remoulding of soft sediments generated mega-scale glacial lineations and drumlins that hold the key to understanding glacier dynamics. The subglacial environment is envisaged as a four-dimensional mosaic of stable and deforming spots transient in time and space whose impact is embedded in the properties of sediment/landform systems.

Piotrowski, Jan A.

2014-05-01

57

Current sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-Frequency Assisted Discharge  

NASA Technical Reports Server (NTRS)

The inductive formation of current sheets in a conical theta pinch FARAD (Faraday Accelerator with Radio-frequency Assisted Discharge) thruster is investigated experimentally with time-integrated photography. The goal is to help in understanding the mechanisms and conditions controlling the strength and extent of the current sheet, which are two indices important for FARAD as a propulsion concept. The profiles of these two indices along the inside walls of the conical acceleration coil are assumed to be related to the profiles of the strength and extent of the luminosity pattern derived from photographs of the discharge. The variations of these profiles as a function of uniform back-fill neutral pressure (with no background magnetic field and all parameters held constant) provided the first clues on the nature and qualitative dependencies of current sheet formation. It was found that there is an optimal pressure for which both indices reach a maximum and that the rate of change in these indices with pressure differs on either side of this optimal pressure. This allowed the inference that current sheet formation follows a Townsend-like breakdown mechanism modified by the existence of a finite pressure-dependent radio-frequency-generated electron density background. The observation that the effective location of the luminosity pattern favors the exit-half of the conical coil is explained as the result of the tendency of the inductive discharge circuit to operate near its minimal self-inductance. Movement of the peak in the luminosity pattern towards the upstream side of the cone with increasing pressure is believed to result from the need of the circuit to compensate for the increase in background plasma resistivity due to increasing pressure.

Hallock, Ashley K.; Choueiri, Edgar Y.; Polzin, Kurt A.

2007-01-01

58

Efficient traversal of beta-sheet protein folding pathways using ensemble models.  

PubMed

Molecular dynamics (MD) simulations can now predict ms-timescale folding processes of small proteins; however, this presently requires hundreds of thousands of CPU hours and is primarily applicable to short peptides with few long-range interactions. Larger and slower-folding proteins, such as many with extended ?-sheet structure, would require orders of magnitude more time and computing resources. Furthermore, when the objective is to determine only which folding events are necessary and limiting, atomistic detail MD simulations can prove unnecessary. Here, we introduce the program tFolder as an efficient method for modelling the folding process of large ?-sheet proteins using sequence data alone. To do so, we extend existing ensemble ?-sheet prediction techniques, which permitted only a fixed anti-parallel ?-barrel shape, with a method that predicts arbitrary ?-strand/?-strand orientations and strand-order permutations. By accounting for all partial and final structural states, we can then model the transition from random coil to native state as a Markov process, using a master equation to simulate population dynamics of folding over time. Thus, all putative folding pathways can be energetically scored, including which transitions present the greatest barriers. Since correct folding pathway prediction is likely determined by the accuracy of contact prediction, we demonstrate the accuracy of tFolder to be comparable with state-of-the-art methods designed specifically for the contact prediction problem alone. We validate our method for dynamics prediction by applying it to the folding pathway of the well-studied Protein G. With relatively very little computation time, tFolder is able to reveal critical features of the folding pathways which were only previously observed through time-consuming MD simulations and experimental studies. Such a result greatly expands the number of proteins whose folding pathways can be studied, while the algorithmic integration of ensemble prediction with Markovian dynamics can be applied to many other problems. PMID:21958108

Shenker, Solomon; O'Donnell, Charles W; Devadas, Srinivas; Berger, Bonnie; Waldispühl, Jérôme

2011-11-01

59

Groundwater flow beneath ice sheets: Part II — Its impact on glacier tectonic structures and moraine formation  

NASA Astrophysics Data System (ADS)

Meltwater flowing as groundwater from beneath the margin of an ice sheet determines the distribution of sub-surface heads and effective pressures. A subglacial groundwater flow model is used, together with an ice sheet loading model, to compute the magnitudes and directions of the principal effective stresses in the subsurface, from which the distribution of different types of sub-surface failure in the subglacial and proglacial zones are deduced. Zones of hydrofracturing, shear fracture and pervasive shear failure are distinguished. Beneath the ice sheet divide area, intact rocks of high tensile strength may fail. Hydrofracturing and liquefaction are two coupled processes which lead to the formation of upward-filled and downward-filled sediment dykes and till wedges. Quicksand conditions are developed where strong vertical seepage pressures occur, producing sediment diapirism. It is suggested that subglacial permeability magnitude may be the product of a self organising process. Certain types of moraine (extrusion moraines) are suggested to be a consequence of upward movement and surface extrusion of sediment driven by rising groundwater. It is suggested that groundwater over pressure associated with narrow proglacial permafrost plates are conductive to the formation of large push moraines, and that many large ancient and modern examples are produced in this setting.

Boulton, G. S.; Caban, P.

60

Possible role of midcrustal igneous sheet intrusions in cratonic arch formation  

NASA Astrophysics Data System (ADS)

Factors controlling widespread cratonic arch formation across western North America from the Early Paleozoic to the Middle Mesozoic remain poorly understood. While a number of causes, such as mantle hot spots, lithospheric contraction, mantle flow, and lithospheric flexure due to surface loading, have been suggested to explain the localized uplift of basement blocks on otherwise tectonically quiescent margins, a variety of mechanisms may be at work. Here, we test the hypothesis that seismically detected packages of discrete midcrustal igneous sheet intrusions impart rheological contrasts within the crust, which act as seeds for cratonic arch formation in the presence of weak intraplate compression, using finite element modeling of intraplate deformation. We find that the seismically resolved sills can generate significant surface uplift in the presence of modest strain rates over reasonable orogenic timescales. Cratonic arch formation would be enhanced in the presence of additional thin, seismically unresolvable sills. While midcrustal sheet intrusions may be just one of many factors influencing cratonic arch formation, their presence in northern Alberta, Canada, can help explain the asymmetric configuration of the well-studied Peace River Arch.

Welford, J. K.; Hearn, E. H.; Clowes, R. M.

2007-10-01

61

Inhibition of fibril formation in beta-amyloid peptide by a novel series of benzofurans.  

PubMed Central

A series of benzofuran derivatives have been identified as inhibitors of fibril formation in the beta-amyloid peptide. The activity of these compounds has been assessed by a novel fibril-formation-specific immunoassay and for their effects on the production of a biologically active fibril product. The inhibition afforded by the compounds seems to be associated with their binding to beta-amyloid, as identified by scintillation proximity binding assay. Binding assays and NMR studies also indicate that the inhibition is associated with self-aggregation of the compounds. There is a close correlation between the activity of the benzofurans as inhibitors of fibril formation and their ability to bind to beta-amyloid. Non-benzofuran inhibitors of the fibril formation process do not seem to bind to the same site on the beta-amyloid molecule as the benzofurans. Thus a specific recognition site might exist for benzofurans on beta-amyloid, binding to which seems to interfere with the ability of the peptide to form fibrils. PMID:10229684

Howlett, D R; Perry, A E; Godfrey, F; Swatton, J E; Jennings, K H; Spitzfaden, C; Wadsworth, H; Wood, S J; Markwell, R E

1999-01-01

62

Inhibition of Fibril Formation of Beta-Amyloid Peptides  

Microsoft Academic Search

Alzheimer's, Parkinson's, Huntington's, type II diabetes , and Mad Cow disease, or Cystic fi- brosis, these apparently unrelated diseases, the so-calle d protein structural diseases, are found to be a result of protein misfolding. Understanding the role of molecular inhibitors in formation of amyloid fibrils plays an important role in finding proper tr eatments to those structural dis- eases. In

Nguyen Sy Lam; Maksim Kouza; Hoang Zung

63

The response regulator OmpR oligomerizes via beta-sheets to form head-to-head dimers.  

PubMed

In Escherichia coli, the EnvZ/OmpR two-component regulatory system regulates expression of the porin genes ompF and ompC in response to changes in osmolarity. It has recently become apparent that OmpR functions as a global regulator, by regulating the expression of many genes in addition to the porin genes. OmpR consists of two domains; phosphorylation of the N-terminal receiver domain increases DNA binding affinity of the C-terminal domain and vice versa. Many response regulators including PhoB and FixJ dimerize upon phosphorylation. Here, we demonstrate that OmpR dimerization is stimulated by phosphorylation or by DNA binding. The dimerization interface revealed here was unanticipated and had previously not been predicted. Using the accepted head-to-tail tandem-binding model as a guide, we set out to examine the intermolecular interactions between OmpR dimers bound to DNA by protein-protein cross-linking methods. Surprisingly, amino acid positions that we expected to form cross-linked dimers did not. Conversely, positions predicted not to form dimers did. Because of these results, we designed a series of 23 cysteine-substituted OmpR mutants that were used to investigate dimer interfaces formed via the beta-sheet region. This four-stranded beta-sheet is a unique feature of the OmpR group of winged helix-turn-helix proteins. Many of the cysteine-substituted mutants are dominant to wild-type OmpR, are phosphorylated by acetyl phosphate as well as the cognate kinase EnvZ, and the cross-linked proteins are capable of binding to DNA. Our results are consistent with a model in which OmpR binds to DNA in a head-to-head orientation, in contrast to the previously proposed asymmetric head-to-tail model. They also raise the possibility that OmpR may be capable of adopting more than one orientation as it binds to a vast array of genes to activate or repress transcription. PMID:15979641

Maris, Ann E; Walthers, Don; Mattison, Kirsten; Byers, Nicole; Kenney, Linda J

2005-07-29

64

alpha_1Antichymotrypsin Regulates Alzheimer beta-Amyloid Peptide Fibril Formation  

Microsoft Academic Search

The major component of the cerebral plaques in Alzheimer disease is the beta-amyloid peptide, but serine proteinase inhibitors like alpha_1-antichymotrypsin (ACT) are also present. Their role in the pathogenesis of amyloid formation is unsettled. In addition to their function as proteinase inhibitors, serine proteinase inhibitors can interact with various hydrophobic compounds, a reaction accompanied by a transition from the stressed

Sten Eriksson; Sabina Janciauskiene; Lars Lannfelt

1995-01-01

65

Heliospheric plasma sheets  

Microsoft Academic Search

As a high-beta feature on scales of hours or less, the heliospheric plasma sheet (HPS) encasing the heliospheric current sheet shows a high degree of variability. A study of 52 sector boundaries identified in electron pitch angle spectrograms in Wind data from 1995 reveals that only half concur with both high-beta plasma and current sheets, as required for an HPS.

N. U. Crooker; C.-L. Huang; S. M. Lamassa; D. E. Larson; S. W. Kahler; H. E. Spence

2004-01-01

66

Phosphoinositide 3-kinase p85beta regulates invadopodium formation  

PubMed Central

ABSTRACT The acquisition of invasiveness is characteristic of tumor progression. Numerous genetic changes are associated with metastasis, but the mechanism by which a cell becomes invasive remains unclear. Expression of p85?, a regulatory subunit of phosphoinositide-3-kinase, markedly increases in advanced carcinoma, but its mode of action is unknown. We postulated that p85? might facilitate cell invasion. We show that p85? localized at cell adhesions in complex with focal adhesion kinase and enhanced stability and maturation of cell adhesions. In addition, p85? induced development at cell adhesions of an F-actin core that extended several microns into the cell z-axis resembling the skeleton of invadopodia. p85? lead to F-actin polymerization at cell adhesions by recruiting active Cdc42/Rac at these structures. In accordance with p85? function in invadopodium-like formation, p85? levels increased in metastatic melanoma and p85? depletion reduced invadopodium formation and invasion. These results show that p85? enhances invasion by inducing cell adhesion development into invadopodia-like structures explaining the metastatic potential of tumors with increased p85? levels. PMID:25217619

Cariaga-Martinez, Ariel E.; Cortes, Isabel; Garcia, Esther; Perez-Garcia, Vicente; Pajares, Maria J.; Idoate, Miguel A.; Redondo-Munoz, Javier; Anton, Ines M.; Carrera, Ana C.

2014-01-01

67

Low cost fabrication of sheet structure using a new beta titanium alloy, Ti-15V-3Cr-3Al-3Sn  

NASA Technical Reports Server (NTRS)

Development efforts have been undertaken to improve the processing and structural efficiencies of advanced cold-formable beta Ti alloys, using the standard, hot-formed and rivetted construction of Ti-6Al-4V sheet structures as a basis for comparison. Ti-15V-3Cr-3Al-3Sn (Ti-15-3) beta alloy is formable, brazable and weldable in the solution-treated condition, and after aging displays mechanical properties suitable for postulated service in the -65 to 600 F temperature range. A novel methodology using cold-formed Ti-15-3 stringers and Ti-6Al-4V face sheets that are joined by means of an out-of-furnace isothermal brazing process, followed by low temperature aging, can reduce production costs by as much as 28 per cent. Structural efficiency has been demonstrated in room and elevated temperature crippling tests of small skin-stringer assemblies.

Kaneko, R. S.; Davis, G. W.; Woods, C. A.; Royster, D. M.

1982-01-01

68

Identification and characterization of the antimicrobial peptide corresponding to C-terminal beta-sheet domain of tenecin 1, an antibacterial protein of larvae of Tenebrio molitor.  

PubMed Central

An active fragment was identified from tenecin 1, an antibacterial protein belonging to the insect defensin family, by synthesizing the peptides corresponding to the three regions of tenecin 1. Only the fragment corresponding to the C-terminal beta-sheet domain showed activity against fungi as well as Gram-positive and Gram-negative bacteria, whereas tenecin 1, the native protein, showed activity only against Gram-positive bacteria. CD spectra indicated that each fragment in a membrane-mimetic environment might adopt a secondary structure corresponding to its region in the protein. The leakage of dye from liposomes induced by this fragment suggested that this fragment acts on the membrane of pathogens as a primary mode of action. A comparison between the structure and the activity of each fragment indicated that a net positive charge was a prerequisite factor for activity. To the best of our knowledge this is the first report in which the fragment corresponding to the beta-sheet region in antibacterial proteins, which consists of alpha-helical and beta-sheet regions, has been identified as a primary active fragment. PMID:9693108

Lee, K H; Hong, S Y; Oh, J E; Kwon, M; Yoon, J H; Lee, J; Lee, B L; Moon, H M

1998-01-01

69

Ballooning instability at the plasma sheet–lobe interface and its implications for polar arc formation  

Microsoft Academic Search

Huang et al. (1987, 1989) reported hot filaments of plasma sheet origin filling the magnetospheric lobes during northward interplanetary magnetic field (IMF). On the other hand, cold plasma transients of presumably lobe origin are often observed in the plasma sheet. These features can be interpreted in terms of plasma exchange at the plasma sheet–lobe interface (PSLI) proceeding in a filamentary

I. V. Golovchanskaya; A. Kullen; Y. P. Maltsev; H. Biernat

2006-01-01

70

Ballooning instability at the plasma sheet-lobe interface and its implications for polar arc formation  

Microsoft Academic Search

Huang et al. (1987, 1989) reported hot filaments of plasma sheet origin filling the magnetospheric lobes during northward interplanetary magnetic field (IMF). On the other hand, cold plasma transients of presumably lobe origin are often observed in the plasma sheet. These features can be interpreted in terms of plasma exchange at the plasma sheet-lobe interface (PSLI) proceeding in a filamentary

I. V. Golovchanskaya; A. Kullen; Y. P. Maltsev; H. Biernat

2006-01-01

71

Beta-catenin signaling pathway is crucial for bone morphogenetic protein 2 to induce new bone formation.  

PubMed

Endochondral ossification is recapitulated during bone morphogenetic protein (BMP)-induced ectopic bone formation. Although BMP and beta-catenin have been investigated in bone development and in mesenchymal cells, how they interact in this process is not clear. We implanted recombinant BMP-2 into the muscle of mice to investigate the effect of beta-catenin signaling on BMP-induced in vivo endochondral bone formation. BMP-2 induced expression of several Wnt ligands and their receptors and also activated beta-catenin-mediated T cell factor-dependent transcriptional activity. An adenovirus expressing Dickkopf-1 (Dkk-1, an inhibitor of canonical Wnt pathway) inhibited beta-catenin signaling and endochondral bone formation. Interestingly, Dkk-1 inhibited both chondrogenesis and osteogenesis. Likewise, mice expressing conditional beta-catenin null alleles also displayed an inhibition of BMP-induced chondrogenesis and osteogenesis. This is in contrast to studies of embryonic skeletogenesis, which demonstrate that beta-catenin is required for osteogenesis but is dispensable for chondrogenesis. These findings suggest that embryonic development pathways are not always recapitulated during post-natal regenerative processes, and the biochemical pathways utilized to regulate cell differentiation may be different. During in vivo ectopic bone formation, BMP-2 induces beta-catenin-mediated signaling through Wnt ligands, and beta-catenin is required for both chondrogenesis and osteogenesis. PMID:17085452

Chen, Yan; Whetstone, Heather C; Youn, Andrew; Nadesan, Puviindran; Chow, Edwin C Y; Lin, Alvin C; Alman, Benjamin A

2007-01-01

72

Nonlinear evolution of three-dimensional instabilities of thin and thick electron scale current sheets: Plasmoid formation and current filamentation  

NASA Astrophysics Data System (ADS)

Nonlinear evolution of three dimensional electron shear flow instabilities of an electron current sheet (ECS) is studied using electron-magnetohydrodynamic simulations. The dependence of the evolution on current sheet thickness is examined. For thin current sheets (half thickness =de=c /?pe), tearing mode instability dominates. In its nonlinear evolution, it leads to the formation of oblique current channels. Magnetic field lines form 3-D magnetic spirals. Even in the absence of initial guide field, the out-of-reconnection-plane magnetic field generated by the tearing instability itself may play the role of guide field in the growth of secondary finite-guide-field instabilities. For thicker current sheets (half thickness ˜5 de), both tearing and non-tearing modes grow. Due to the non-tearing mode, current sheet becomes corrugated in the beginning of the evolution. In this case, tearing mode lets the magnetic field reconnect in the corrugated ECS. Later thick ECS develops filamentary structures and turbulence in which reconnection occurs. This evolution of thick ECS provides an example of reconnection in self-generated turbulence. The power spectra for both the thin and thick current sheets are anisotropic with respect to the electron flow direction. The cascade towards shorter scales occurs preferentially in the direction perpendicular to the electron flow.

Jain, Neeraj; Büchner, Jörg

2014-07-01

73

Formation and transport of low-voltage, space-charge dominated sheet electron beams for high-power microwave devices  

SciTech Connect

Sheet electron beams have the potential to make possible higher power sources of microwave radiation due to their ability to transport high currents, at reduced current densities, through a single narrow RF interaction circuit. The authors will discuss experimental investigations of the formation of an elliptical sheet beam using magnet quadrupoles and a round-beam electron gun. Features of this configuration include a low-cost, commercially available Pierce gun and a lens system consisting of four tunable magnetic quadrupoles with modest field gradients. Three-dimensional envelope and particle-in-cell simulations indicate that this method can generate highly elliptic output beams, with variability in final beam size, for laboratory experiments on sheet beam transport. They also will present the results of particle-in-cell simulations of the transport of sheet beams in long-period offset-pole periodic magnet arrays. While the stability of sheet beams in short-period arrays has previously been established, the extension to longer magnet periods indicate that side-focusing of space-charge dominated sheet beams is more problematic than beam stability. However, long-term (> 20 periods) stable transport is demonstrated for {lambda}{sub m} = 1 cm for a 2 A, 10 kV elliptical beam with a = 2.7 cm and b = 0.05 cm.

Basten, M.A.; Booske, J.H.; Louis, L.J.; Joe, J.; Scharer, J.E. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Electrical and Computer Engineering

1996-12-31

74

Interchange motion as a transport mechanism for formation of cold-dense plasma sheet  

NASA Astrophysics Data System (ADS)

evaluate whether interchange motion can provide the transport for the formation of the cold-dense plasma sheet in the near-Earth region, we present an event of cold-dense plasma sheet observed by five THEMIS probes after the interplanetary magnetic field turned northward, as well as their comparisons with the simulation results from the Rice Convection Model (RCM) combined with a modified Dungey force-balanced magnetic field solver. The observations of cold-dense plasma at different locations show quite different characteristics: (1) closer to the flank, the appearance is more periodic and exhibits larger fluctuations in plasma moments and magnetic field; (2) further away from the flank, the cold plasma appears later; (3) in the mixture with the cold plasma, the decrease in high-energy particle fluxes becomes less significant further away from the flank; (4) there is energy-dispersion in the cold particles at some locations; and (5) near the magnetopause, the fluctuations have the characteristics of the Kelvin-Helmholtz (K-H) vortices and the colder-denser plasma is likely to have lower entropy. In the RCM simulations, lower entropy plasma consisting of colder-denser ions and electrons was periodically released locally at the outer boundary to represent the plasma created within a K-H vortex. This lower entropy perturbation is interchange unstable and the resulting interchange motion through the magnetosphere-ionosphere coupling pushes the colder-denser plasma radially inward. The simulated particle energy spectrums at different locations qualitatively reproduce the observations, strongly suggesting that the seemingly different characteristics of cold-dense plasma observed by different probes are all a result of the same interchange-related transport mechanism.

Wang, Chih-Ping; Gkioulidou, Matina; Lyons, Larry R.; Xing, Xiaoyan; Wolf, Richard A.

2014-10-01

75

The role of the turn in beta-hairpin formation during WW domain folding.  

PubMed

The folding of WW domains is rate limited by formation of a beta-hairpin comprising residues from strands 1 and 2. Residues in the turn of this hairpin have reported Phi-values for folding close to 1 and have been proposed to nucleate folding. High Phi-values do not necessarily imply that the energetics of formation are a driving force for initiating folding. We demonstrate by NMR studies and molecular dynamics simulations that the first turn of the hYAP, FBP28, and PIN1 WW domains is structurally dynamic and solvent exposed in the native and folding transition states. It is, therefore, unlikely that the formation of the beta-turn per se provides the energetic driving force for hairpin folding. It is more likely that the turn acts as an easily formed hinge that facilitates the formation of the hairpin; it is a nucleus as defined by the nucleation-condensation mechanism whereby a diffuse nucleus is stabilized by associated interactions. PMID:17766370

Sharpe, Tim; Jonsson, Amanda L; Rutherford, Trevor J; Daggett, Valerie; Fersht, Alan R

2007-10-01

76

Mechanism of the activation of proteinase inhibitor synthesis by systemin involves beta-sheet structure, a specific DNA-binding protein domain.  

PubMed

We analyzed a tertiary structure of systemin, the first identified polypeptide plant hormone, using two-dimensional NMR spectroscopy. From these data and molecular dynamics calculations we concluded that the peptide can adopt a Z-like-beta-sheet structure, which has previously been found in many specific DNA-binding proteins. Using DNA-cellulose affinity chromatography, we showed that systemin binds strongly to DNA. We suggest that the specific systemin-DNA interaction, particularly in a promoter region of the proteinase inhibitors, could effect gene expression and thus explain the biological activity of systemin. PMID:7577230

Slósarek, G; Kalbitzer, H R; Mucha, P; Rekowski, P; Kupryszewski, G; Giel-Pietraszuk, M; Szyma?ski, M; Barciszewski, J

1995-01-01

77

Formation of a very thin current sheet in the near-earth magnetotail and the explosive growth phase of substorms  

NASA Technical Reports Server (NTRS)

A magnetofricional method is used to construct two-dimensional MHD equilibria of the Earth's magnetosphere for a given distribution of entropy functions(S = pV(exp gamma), where p is the plasma pressure and V is the tube volume per unit magnetic flux. It is found that a very thin current sheet with B (sub zeta) is less than 0.5 nu T and thickness less than 1000 km can be formed in the near-earth magnetotail (x is approximately -8 to -20R(sub e) during the growth phase of substorm. The tail current sheets are found to become thinner as the entropy or the entropy gradient increases. It is suggested that the new entropy anti-diffusion instability associated with plasma transport across field lines leads to magnetic field dipolarization and accelerates the formation of thin current sheet, which may explain the observed explosive growth phase of substorms.

Lee, L. C.; Zhang, L.; Choe, G. S.; Cai, H. J.

1995-01-01

78

Analysis of Nugget Formation During Resistance Spot Welding on Dissimilar Metal Sheets of Aluminum and Magnesium Alloys  

NASA Astrophysics Data System (ADS)

The nugget formation of resistance spot welding (RSW) on dissimilar material sheets of aluminum and magnesium alloys was studied, and the element distribution, microstructure, and microhardness distribution near the joint interface were analyzed. It was found that the staggered high regions at the contact interface of aluminum and magnesium alloy sheets, where the dissimilar metal melted together, tended to be the preferred nucleation regions of nugget. The main technical problem of RSW on dissimilar metal sheets of aluminum and magnesium alloys was the brittle-hard Al12Mg17 intermetallic compounds distributed in the nugget, with hardness much higher than either side of the base materials. Microcracks tended to generate at the interface of the nugget and base materials, which affected weld quality and strength.

Luo, Yi; Li, Jinglong

2014-10-01

79

Inducing ?-Sheets Formation in Synthetic Spider Silk Fibers by Aqueous Post-Spin Stretching  

PubMed Central

As a promising biomaterial with numerous potential applications, various types of synthetic spider silk fibers have been produced and studied in an effort to produce manmade fibers with mechanical and physical properties comparable to those of native spider silk. In this study, two recombinant proteins based on Nephila clavipes Major ampullate Spidroin 1 (MaSp1) consensus repeat sequence were expressed and spun into fibers. Mechanical test results showed that fiber spun from the higher molecular weight protein had better overall mechanical properties (70 KD versus 46 KD), whereas postspin stretch treatment in water helped increase fiber tensile strength significantly. Carbon-13 solid-state NMR studies of those fibers further revealed that the postspin stretch in water promoted protein molecule rearrangement and the formation of ?-sheets in the polyalanine region of the silk. The rearrangement correlated with improved fiber mechanical properties and indicated that postspin stretch is key to helping the spider silk proteins in the fiber form correct secondary structures, leading to better quality fibers. PMID:21574576

Hinman, Michael B.; Holland, Gregory P.; Yarger, Jeffery L.; Lewis, Randolph V.

2012-01-01

80

Inducing ?-sheets formation in synthetic spider silk fibers by aqueous post-spin stretching.  

PubMed

As a promising biomaterial with numerous potential applications, various types of synthetic spider silk fibers have been produced and studied in an effort to produce man-made fibers with mechanical and physical properties comparable to those of native spider silk. In this study, two recombinant proteins based on Nephila clavipes Major ampullate Spidroin 1 (MaSp1) consensus repeat sequence were expressed and spun into fibers. Mechanical test results showed that fiber spun from the higher molecular weight protein had better overall mechanical properties (70 KD versus 46 KD), whereas postspin stretch treatment in water helped increase fiber tensile strength significantly. Carbon-13 solid-state NMR studies of those fibers further revealed that the postspin stretch in water promoted protein molecule rearrangement and the formation of ?-sheets in the polyalanine region of the silk. The rearrangement correlated with improved fiber mechanical properties and indicated that postspin stretch is key to helping the spider silk proteins in the fiber form correct secondary structures, leading to better quality fibers. PMID:21574576

An, Bo; Hinman, Michael B; Holland, Gregory P; Yarger, Jeffery L; Lewis, Randolph V

2011-06-13

81

Cell sheet transplantation of cultured mesenchymal stem cells enhances bone formation in a rat nonunion model  

Microsoft Academic Search

Orthopedic surgeons have long been troubled by cases involving nonunion of fractured bones. This study aimed to enhance bone union by cell sheet transplantation of mesenchymal stem cells. A nonunion model was made in rat femur, and rat bone marrow cells were cultured in medium containing dexamethasone and ascorbic acid phosphate to create a cell sheet that could be scraped

Akifumi Nakamura; Manabu Akahane; Hideki Shigematsu; Mika Tadokoro; Yusuke Morita; Hajime Ohgushi; Yoshiko Dohi; Tomoaki Imamura; Yasuhito Tanaka

2010-01-01

82

Protein Secondary Structures (alpha-helix and beta-sheet) at a Cellular Levle and Protein Fractions in Relation to Rumen Degradation Behaviours of Protein: A New Approach  

SciTech Connect

Studying the secondary structure of proteins leads to an understanding of the components that make up a whole protein, and such an understanding of the structure of the whole protein is often vital to understanding its digestive behaviour and nutritive value in animals. The main protein secondary structures are the {alpha}-helix and {beta}-sheet. The percentage of these two structures in protein secondary structures influences protein nutritive value, quality and digestive behaviour. A high percentage of {beta}-sheet structure may partly cause a low access to gastrointestinal digestive enzymes, which results in a low protein value. The objectives of the present study were to use advanced synchrotron-based Fourier transform IR (S-FTIR) microspectroscopy as a new approach to reveal the molecular chemistry of the protein secondary structures of feed tissues affected by heat-processing within intact tissue at a cellular level, and to quantify protein secondary structures using multicomponent peak modelling Gaussian and Lorentzian methods, in relation to protein digestive behaviours and nutritive value in the rumen, which was determined using the Cornell Net Carbohydrate Protein System. The synchrotron-based molecular chemistry research experiment was performed at the National Synchrotron Light Source at Brookhaven National Laboratory, US Department of Energy. The results showed that, with S-FTIR microspectroscopy, the molecular chemistry, ultrastructural chemical make-up and nutritive characteristics could be revealed at a high ultraspatial resolution ({approx}10 {mu}m). S-FTIR microspectroscopy revealed that the secondary structure of protein differed between raw and roasted golden flaxseeds in terms of the percentages and ratio of {alpha}-helixes and {beta}-sheets in the mid-IR range at the cellular level. By using multicomponent peak modelling, the results show that the roasting reduced (P <0.05) the percentage of {alpha}-helixes (from 47.1% to 36.1%: S-FTIR absorption intensity), increased the percentage of {beta}-sheets (from 37.2% to 49.8%: S-FTIR absorption intensity) and reduced the {alpha}-helix to {beta}-sheet ratio (from 0.3 to 0.7) in the golden flaxseeds, which indicated a negative effect of the roasting on protein values, utilisation and bioavailability. These results were proved by the Cornell Net Carbohydrate Protein System in situ animal trial, which also revealed that roasting increased the amount of protein bound to lignin, and well as of the Maillard reaction protein (both of which are poorly used by ruminants), and increased the level of indigestible and undegradable protein in ruminants. The present results demonstrate the potential of highly spatially resolved synchrotron-based infrared microspectroscopy to locate 'pure' protein in feed tissues, and reveal protein secondary structures and digestive behaviour, making a significant step forward in and an important contribution to protein nutritional research. Further study is needed to determine the sensitivities of protein secondary structures to various heat-processing conditions, and to quantify the relationship between protein secondary structures and the nutrient availability and digestive behaviour of various protein sources. Information from the present study arising from the synchrotron-based IR probing of the protein secondary structures of protein sources at the cellular level will be valuable as a guide to maintaining protein quality and predicting digestive behaviours.

Yu,P.

2007-01-01

83

Resorption of, and bone formation from, new beta-tricalcium phosphate-monocalcium phosphate cements: an in vivo study.  

PubMed

Hard cylinders (4.7 x 10 mm) of two kinds of beta-tricalcium phosphate-monocalcium phosphate monohydrate-calcium sulfate hemihydrate (beta-TCP-MCPM-CSH) cements with and without beta-TCP granules (500-1000 microns) were implanted into holes drilled in rabbit femoral condyles for up to 16 weeks. Empty cavities were used as control. Cement resorption and new bone formation in the cylinders were evaluated with contact microradiography and quantified through an automatic image analysis system. At 4 weeks, both kinds of cement cylinders were surrounded by new bone. At 8 weeks, except for beta-TCP granules, both cement cylinders were almost completely resorbed and replaced by bone tissue. At 16 weeks the bone in the cavities of both cements recovered a trabecular pattern, but only the bone trabeculae in the initial cavity of the cement with beta-TCP granules became thick and mature. However, the cavities of the empty control were still empty and large. These results show that the beta-TCP-MCPM-CSH cements stimulate bone formation and are rapidly replaced by bone tissue. When added with nonresorbable beta-TCP granules, this cement maintains bone formation for a longer time. PMID:9019484

Ohura, K; Bohner, M; Hardouin, P; Lemaître, J; Pasquier, G; Flautre, B

1996-02-01

84

Polymerized cyclomaltoheptaose (beta-cyclodextrin, beta-CDn) inclusion complex formation with chlorogenic acid: solvent effects on thermochemistry and enthalpy-entropy compensation.  

PubMed

The inclusion of chlorogenic acid (CA) by epichlorohydrin-polymerized cyclomaltoheptaose (beta-cyclodextrin, beta-CDn) was studied with regard to temperature, solvent, and water activity aH2O approximately mole fraction = XH2O = 0.8-1 using MeOH as the diluent; 0.1 M sodium phosphate buffer). We discovered that the extreme convex curvature in K (the apparent stability constant) as a function of temperature was nearly eliminated at the lowest XH2O. The latter finding argues that this unusual CD behavior in aqueous media was due to perturbations in beta-CD's spatial organization in the polymeric matrix with temperature. Related to this we found, from the dependence of K on XH2O (K = K'XzH2O), that the beta-CDn.CA complex's stoichiometric coefficient, z, for water, varied between 5 and 8, depending on the temperature of the solution (K' = 400-800 M-1; T approximately 295-315 K). Our determinations of z were similar to those reported previously for beta-CD.(+)-limonene (z approximately 7), soluble beta-CD.CA (z approximately 6) or obtained by molecular dynamics calculations for beta-CD.CA reported herein (z approximately 5). However, beta-CDn.CA's z values did show a significant positive correlation with temperature not evident in equivalent solution experiments. Calculations of delta H and delta S at various XH2O values show linear enthalpy-entropy compensation (delta H plotted against delta S) but with a slope (Tc = theta delta H/theta delta S approximately 228 K) significantly less than Tc values determined from either standard aqueous thermodynamic experiments (Tc approximately 305 K on either beta-CD or beta-CDn) or variable XH2O (Tc approximately 272 K) experiments. To the best of our knowledge, this is the smallest Tc value detected in a multitude of CD.guest studies. This evident solvent effect on Tc strongly argues that the chemical part process of inclusion complex formation involves changes in the solvation of the beta-CDn's binding site. PMID:8721737

Irwin, P L; King, G; Hicks, K B

1996-02-28

85

Spontaneous formation of stringlike clusters and smectic sheets for colloidal rods confined in thin wedgelike gaps.  

PubMed

Monodispersed colloidal rods of ?-FeOOH with sizes ranging from 270 to 580 nm in length and 50 to 80 nm in width were synthesized. Narrow wedgelike gaps (0 to 700 nm in height) were formed around the inner bottom edge of the suspension glass cells. Optical microscopic observations revealed the formation of stringlike clusters of the rods and smectic sheets (by spontaneous side-by-side clustering of the strings) in the isotropic phase of the rod suspensions confined in narrow gaps; the electrolyte (HCl) concentrations of the suspensions are 5-40 mM, at which inter-rod interactions are attractive. The strings exhibit different colors that were used to investigate the structures of the strings with the help of interference color theory for thin films. The results are as follows. (1) The rods, lying flat on the gap bottom, are connected side-by-side and stacked upward to form stringlike clusters with different thicknesses depending on the gap height. (2) The stacking numbers (N(sr)) of the rods are estimated to be 1-5. With N(sr) increasing from 2 to 5, the volume fractions (?) of the rods in the strings increased typically from 0.25-0.3 to 0.35-0.42 to reach limiting values (close to the ? values of the rods in the bulk smectic phase). (3) Unexpected low-? strings are found in regions with an intermediate height in the gaps. These behaviors of ? may be caused by thermal fluctuations of the strings. PMID:23876087

Maeda, Hideatsu; Maeda, Yoshiko

2013-08-20

86

Formation of Sheeting Joints as a Result of Compression Parallel to Convex Surfaces, With Examples from Yosemite National Park, California  

NASA Astrophysics Data System (ADS)

The formation of sheeting joints has been an outstanding problem in geology. New observations and analyses indicate that sheeting joints develop in response to a near-surface tension induced by compressive stresses parallel to a convex slope (hypothesis 1) rather than by removal of overburden by erosion, as conventionally assumed (hypothesis 2). Opening mode displacements across the joints together with the absence of mineral precipitates within the joints mean that sheeting joints open in response to a near-surface tension normal to the surface rather than a pressurized fluid. Consideration of a plot of this tensile stress as a function of depth normal to the surface reveals that a true tension must arise in the shallow subsurface if the rate of that tensile stress change with depth is positive at the surface. Static equilibrium requires this rate (derivative) to equal P22 k2 + P33 k3 - ? g cos?, where k2 and k3 are the principal curvatures of the surface, P22 and P33 are the respective surface- parallel normal stresses along the principal curvatures, ? is the material density, g is gravitational acceleration, and ? is the slope. This derivative will be positive and sheeting joints can open if at least one principal curvature is sufficiently convex (negative) and the surface-parallel stresses are sufficiently compressive (negative). At several sites with sheeting joints (e.g., Yosemite National Park in California), the measured topographic curvatures and the measured surface-parallel stresses of about -10 MPa combine to meet this condition. In apparent violation of hypothesis 1, sheeting joints occur locally at the bottom of Tenaya Canyon, one of the deepest glaciated, U-shaped (concave) canyons in the park. The canyon-bottom sheeting joints only occur, however, where the canyon is convex downstream, a direction that nearly coincides with direction of the most compressive stress measured in the vicinity. The most compressive stress acting along the convex downstream curvature promotes the opening of the joints, whereas the compressive stress acting across the U-shaped valley promotes closure of the joints. Apparently the former more than compensates for the latter. Finally, the abundance of sheeting joints on convex ridges, where erosion is a local minimum, coupled with their scarcity in the adjacent concave valleys, where erosion is a local maximum, is consistent with hypothesis 1 but inconsistent with hypothesis 2.

Martel, S. J.

2008-12-01

87

Vitamin C Treatment Promotes Mesenchymal Stem Cell Sheet Formation and Tissue Regeneration by Elevating Telomerase Activity  

PubMed Central

Cell sheet engineering has been developed as an alternative approach to improve mesenchymal stem cell-mediated tissue regeneration. In this study, we found that vitamin C (Vc) was capable of inducing telomerase activity in periodontal ligament stem cells (PDLSCs), leading to the up-regulated expression of extracellular matrix type I collagen, fibronectin, and integrin ?1, stem cell markers Oct4, Sox2, and Nanog as well as osteogenic markers RUNX2, ALP, OCN. Under Vc treatment, PDLSCs can form cell sheet structures because of increased cell matrix production. Interestingly, PDLSC sheets demonstrated a significant improvement in tissue regeneration compared with untreated control dissociated PDLSCs and offered an effective treatment for periodontal defects in a swine model. In addition, bone marrow mesenchymal stem cell sheets and umbilical cord mesenchymal stem cell sheets were also well constructed using this method. The development of Vc-mediated mesenchymal stem cell sheets may provide an easy and practical approach for cell-based tissue regeneration. PMID:22105792

Wei, F.L.; Qu, C.Y.; Song, T.L.; Ding, G.; Fan, Z.P.; Liu, D.Y.; Liu, Y.; Zhang, C.M.; Shi, S.; Wang, S.L.

2011-01-01

88

The effect of low levels of dopants upon the formation and properties of beta-phase molybdenum nitride  

SciTech Connect

The addition of 1 wt% Pd, Au, Ni and Cu dopants has been demonstrated to strongly alter the morphology of beta-phase molybdenum nitride prepared by treatment of MoO{sub 3} with a 3/1 H{sub 2}/N{sub 2} mixture at 750 deg. C. Furthermore, the addition of Pd significantly enhances the surface area and the formation of the nitride phase. It is proposed that the facile formation of molybdenum bronzes in this system is important in this respect. The dopants have also been observed to modify the denitridation characteristics of the beta-phase, with an overall reduction of the proportion of NH{sub 3} formed upon using a 3/1 H{sub 2}/Ar mixture with respect to the undoped sample. - Graphical abstract: Low levels of Pd, Au, Ni and Cu dopant have significant effects upon the morphology, formation and dentitridation characteristics of beta-phase molybdenum nitride.

Cairns, A.G.; Gallagher, J.G. [WestCHEM, Department of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Hargreaves, J.S.J., E-mail: justinh@chem.gla.ac.u [WestCHEM, Department of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Mckay, D. [WestCHEM, Department of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Rico, J.L., E-mail: jlrico@umich.m [Laboratorio de Catalisis, Facultad de Ingenieria Quimica, Universidad Michoacana, Edificio E, CU, Morelia Mich, C.P. 58060 (Mexico); Wilson, K. [WestCHEM, Department of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

2010-03-15

89

Doubling the cross-linking interface of a rationally designed Beta roll Peptide for calcium-dependent proteinaceous hydrogel formation.  

PubMed

We have rationally engineered a stimulus-responsive cross-linking domain based on a repeats-in-toxin (RTX) peptide to enable calcium-dependent formation of supramolecular hydrogel networks. The peptide isolated from the RTX domain is intrinsically disordered in the absence of calcium. In calcium rich environments, the peptide binds Ca(2+) ions and folds into a beta roll (?-roll) secondary structure composed to two parallel ?-sheet faces. Previously, we mutated one of the faces to contain solvent exposed leucine side chains which are localized only in the calcium-bound ?-roll conformation. We demonstrated the ability of this mutant peptide to self-assemble into hydrogels in the presence of calcium with the aid of additional peptide-based cross-linking moieties. Here, we have expanded this approach by engineering both ?-roll faces to contain leucine residues, thereby doubling the cross-linking interface for each monomeric building block. These leucine rich surfaces impart a hydrophobic driving force for self-assembly. Extensive characterization was performed on this double-faced mutant to ensure the retention of calcium affinity and subsequent structural rearrangement similar to that of the wild type domain. We genetically fused an ?-helical leucine zipper capable of forming tetrameric coiled-coil bundles to the peptide and the resulting chimeric protein self-assembles into a hydrogel only in calcium rich environments. Since this new mutant peptide enables cross-linking on both surfaces simultaneously, a higher oligomerization state was achieved. To further investigate the cross-linking capability, we constructed concatemers of the ?-roll with maltose binding protein (MBP), a monomeric globular protein, without the leucine zipper domains. These concatemers show a similar sol-gel transition in response to calcium. Several biophysical techniques were used to probe the structural and mechanical properties of the mutant ?-roll domain and the resulting supramolecular networks including circular dichroism, fluorescence resonance energy transfer, bis-ANS binding, and microrheology. These results demonstrate that the engineered ?-roll peptides can mediate calcium-dependent cross-linking for protein hydrogel formation without the need for any other cross-linking moieties. PMID:25226243

Dooley, Kevin; Bulutoglu, Beyza; Banta, Scott

2014-10-13

90

Formation kinetics and structural features of Beta-amyloid aggregates by sedimented solute NMR.  

PubMed

The accumulation of soluble toxic beta-amyloid (A?) aggregates is an attractive hypothesis for the role of this peptide in the pathology of Alzheimer's disease. We have introduced sedimentation through ultracentrifugation, either by magic angle spinning (in situ) or preparative ultracentrifuge (ex situ), to immobilize biomolecules and make them amenable for solid-state NMR studies (SedNMR). In situ SedNMR is used here to address the kinetics of formation of soluble A? assemblies by monitoring the disappearance of the monomer and the appearance of the oligomers simultaneously. Ex situ SedNMR allows us to select different oligomeric species and to reveal atomic-level structural features of soluble A? assemblies. PMID:23821412

Bertini, Ivano; Gallo, Gianluca; Korsak, Magdalena; Luchinat, Claudio; Mao, Jiafei; Ravera, Enrico

2013-09-23

91

Microwave study of the formation of brine layers on homogeneous saline ice sheets  

Microsoft Academic Search

When sea water freezes into sea ice, brine and pure ice are produced. Due to the effects of the expulsion of brine from the sea ice interior and the wicking action of snow and frost flowers deposited on the air-ice interface, brine may accumulate on the upper ice sheet surface. Brine is a concentrated solution of sea salts and water,

R. G. Onstott; M. P. Madden

1994-01-01

92

On the formation of the tunnel valleys of the southern Laurentide ice sheet  

Microsoft Academic Search

Catastrophic releases of meltwater, produced by basal melting and stored for decades in subglacial reservoirs at high pressure, may have been responsible for eroding the broad, deep tunnel valleys that are common along the margins of some lobes of the southern Laurentide ice sheet. We surmise that these releases began when the high water pressure was transmitted to the margin

Roger Le B. Hooke; Carrie E. Jennings

2006-01-01

93

Current Sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-frequency Assisted  

E-print Network

Discharge IEPC-2007-165 Presented at the 30th International Electric Propulsion Conference, Florence, Italy sheet, which are two in- dices important for FARAD as a propulsion concept. The profiles of these two of these profiles as a function of uniform back-fill neutral pressure (with no background magnetic field and all

Choueiri, Edgar

94

Efficiently engineered cell sheet using a complex of polyethylenimine-alginate nanocomposites plus bone morphogenetic protein 2 gene to promote new bone formation  

PubMed Central

Regeneration of large bone defects is a common clinical problem. Recently, stem cell sheet has been an emerging strategy in bone tissue engineering. To enhance the osteogenic potential of stem cell sheet, we fabricated bone morphogenetic protein 2 (BMP-2) gene-engineered cell sheet using a complex of polyethylenimine–alginate (PEI–al) nanocomposites plus human BMP-2 complementary(c)DNA plasmid, and studied its osteogenesis in vitro and in vivo. PEI–al nanocomposites carrying BMP-2 gene could efficiently transfect bone marrow mesenchymal stem cells. The cell sheet was made by culturing the cells in medium containing vitamin C for 10 days. Assays on the cell culture showed that the genetically engineered cells released the BMP-2 for at least 14 days. The expression of osteogenesis-related gene was increased, which demonstrated that released BMP-2 could effectively induce the cell sheet osteogenic differentiation in vitro. To further test the osteogenic potential of the cell sheet in vivo, enhanced green fluorescent protein or BMP-2-producing cell sheets were treated on the cranial bone defects. The results indicated that the BMP-2-producing cell sheet group was more efficient than other groups in promoting bone formation in the defect area. Our results suggested that PEI–al nanocomposites efficiently deliver the BMP-2 gene to bone marrow mesenchymal stem cells and that BMP-2 gene-engineered cell sheet is an effective way for promoting bone regeneration. PMID:24855355

Jin, Han; Zhang, Kai; Qiao, Chunyan; Yuan, Anliang; Li, Daowei; Zhao, Liang; Shi, Ce; Xu, Xiaowei; Ni, Shilei; Zheng, Changyu; Liu, Xiaohua; Yang, Bai; Sun, Hongchen

2014-01-01

95

Efficiently engineered cell sheet using a complex of polyethylenimine-alginate nanocomposites plus bone morphogenetic protein 2 gene to promote new bone formation.  

PubMed

Regeneration of large bone defects is a common clinical problem. Recently, stem cell sheet has been an emerging strategy in bone tissue engineering. To enhance the osteogenic potential of stem cell sheet, we fabricated bone morphogenetic protein 2 (BMP-2) gene-engineered cell sheet using a complex of polyethylenimine-alginate (PEI-al) nanocomposites plus human BMP-2 complementary(c)DNA plasmid, and studied its osteogenesis in vitro and in vivo. PEI-al nanocomposites carrying BMP-2 gene could efficiently transfect bone marrow mesenchymal stem cells. The cell sheet was made by culturing the cells in medium containing vitamin C for 10 days. Assays on the cell culture showed that the genetically engineered cells released the BMP-2 for at least 14 days. The expression of osteogenesis-related gene was increased, which demonstrated that released BMP-2 could effectively induce the cell sheet osteogenic differentiation in vitro. To further test the osteogenic potential of the cell sheet in vivo, enhanced green fluorescent protein or BMP-2-producing cell sheets were treated on the cranial bone defects. The results indicated that the BMP-2-producing cell sheet group was more efficient than other groups in promoting bone formation in the defect area. Our results suggested that PEI-al nanocomposites efficiently deliver the BMP-2 gene to bone marrow mesenchymal stem cells and that BMP-2 gene-engineered cell sheet is an effective way for promoting bone regeneration. PMID:24855355

Jin, Han; Zhang, Kai; Qiao, Chunyan; Yuan, Anliang; Li, Daowei; Zhao, Liang; Shi, Ce; Xu, Xiaowei; Ni, Shilei; Zheng, Changyu; Liu, Xiaohua; Yang, Bai; Sun, Hongchen

2014-01-01

96

Outer ligament-mediated spray formation of annular liquid sheet by an inner round air stream  

NASA Astrophysics Data System (ADS)

The interfacial jetting phenomena of coaxial air-assisted water jets are studied using high-speed digital camera. Here, an inner round air jet is injected into annular water sheet spray. The experimental photographs show that the outside interface of liquid sheet shoots out large numbers of violent ligaments at high air velocity. The ligament velocity, ligament angle, ligament diameter, fragment size, and distribution are measured and analyzed. There are two kinds of ligament evolution that are breakup and contraction. An empirical model is also proposed for the ligament evolution process. At last, we obtain the criterion of critical Weber number on the ligament breakup based on the experimental results. This suggestion agrees well with the experimental data.

Zhao, Hui; Liu, Hai-Feng; Tian, Xiu-Shan; Xu, Jian-Liang; Li, Wei-Feng; Lin, Kuang-Fei

2014-08-01

97

Observation of Depolarized ZnO(0001) Monolayers: Formation of Unreconstructed Planar Sheets  

SciTech Connect

A novel nonpolar structure of 2 monolayer (ML) thick ZnO(0001) films grown on Ag(111) has been revealed, using surface x-ray diffraction and scanning tunneling microscopy. Zn and O atoms are arranged in planar sheets like in the hexagonal boron-nitride prototype structure. The observed depolarization is accompanied by a significant lateral 1.6% expansion of the lattice parameter and a 3% reduced Zn-O bond length within the sheets. The nonpolar structure stabilizes an atomically flat surface morphology unseen for ZnO surfaces thus far. The transition to the bulk wurtzite structure occurs in the 3-4 ML coverage range, connected to considerable roughening.

Tusche, C.; Meyerheim, H. L.; Kirschner, J. [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Germany)

2007-07-13

98

Semaphorin 3A blocks the formation of pathologic choroidal neovascularization induced by transforming growth factor beta  

PubMed Central

Objective Choroidal neovascularization (CNV) is a major cause of vision loss in retinal diseases such as age-related macular degeneration (AMD). Previously, we demonstrated that semaphorin3A (Sema3A), which is a chemorepellent guidance molecule, inhibited the formation of retina neovascularization. In the present study, we investigated the antiangiogenic effects of Sema3A on transforming growth factor beta (TGF-?) in vitro and in vivo. Methods Enzyme-linked immunosorbent assays (ELISAs) were used to measure the TGF-? levels in the vitreous humor of patients with AMD and controls. Human umbilical vein endothelial cells (HUVECs) were used for the in vitro study, and a laser-induced CNV mouse model was prepared for the in vivo study. The HUVECs were incubated with TGF-? and Sema3A. The proliferation, migration, apoptosis, and tube formation of the cells were then measured using BrdU, Transwell, flow cytometry, and Matrigel assays, respectively, and the SMAD2/3 signaling pathways were analyzed using western blot analysis. The C57BL/6J mouse retina was exposed to a laser to induce choroidal neovascularization (CNV), and Sema3A was injected intravitreously. After 14 days, fundus fluorescein angiography was performed to evaluate the leakage area of the CNV. The vascular endothelial growth factor (VEGF) and TGF-? concentrations in the retina-choroid complex were measured with ELISA. Components of the p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase-1/2 (ERK1/2), c-Jun NH2-terminal kinase (JNK), and SMAD2/3 signaling pathways in the Sema3A-treated groups were analyzed using western blotting. Results In this study, we first verified that the vitreous TGF-? level was higher in patients with neovascular AMD than in the controls. We also showed that Sema3A inhibited TGF-?-induced HUVEC proliferation, migration, and tube formation and inhibited the downstream SMAD2/3 signaling pathway. Sema3A also induced TGF-?-stimulated HUVEC apoptosis and inhibited the response of TGF-? in vitro. In vivo, the TGF-? level was increased in the CNV mouse model. Sema3A not only inhibited laser-induced CNV formation but also inhibited the uptake of VEGF and TGF-?. In the western blot analysis, Sema3A was shown to inhibit the phosphorylation of p38 MAPK, ERK1/2, and JNK and to inhibit the SMAD2/3 signaling pathway after Sema3A treatment in CNV mice. Conclusions Sema3A can be applied as a useful, adjunctive therapeutic strategy for preventing CNV formation. PMID:25352735

Bai, Yujing; Liang, Shuting; Zhao, Min; Huang, Lvzhen; Zhao, Mingwei; Li, Xiaoxin

2014-01-01

99

Formation of graphene sheets through laser exfoliation of highly ordered pyrolytic graphite  

Microsoft Academic Search

Freestanding two-dimensional (2D) few-layer graphene was formed through laser exfoliation of highly ordered pyrolytic graphite, using a pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. Graphene sheets of several nanometers in thickness and micrometers in size were obtained. The laser exfoliation process was investigated at different laser fluences and distances between target and substrate. Three different phases, amorphous carbon, few-layer graphene

Min Qian; Yun Shen Zhou; Yang Gao; Jong Bok Park; Tao Feng; Su Mei Huang; Zhuo Sun; Lan Jiang; Yong Feng Lu

2011-01-01

100

Double layer formation during current sheet disruptions in a reconnection experiment  

NASA Technical Reports Server (NTRS)

When the current density in the center of a neutral sheet is increased to a critical value spontaneous current disruptions are observed. The release of stored magnetic field energy results in a large inductive voltage pulse which drops off inside the plasma in the form of a potential double layer. Particles are energized, microinstabilities are generated, the plasma is thinned, and the current flow is redirected. These laboratory observations qualitatively support recent models of magnetic substorms and solar flares.

Stenzel, R. L.; Gekelman, W.; Wild, N.

1982-01-01

101

Formation of liquid sheets by deposition of droplets on a surface.  

PubMed

Experiments were done to observe the coalescence of highly viscous liquid droplets (87 wt% glycerin-in-water solutions) deposited onto a flat, solid steel plate. Droplets were deposited sequentially in straight lines or square droplet arrays. Droplet center-to-center distance was varied and the final dimensions of lines and sheets measured from photographs. When overlapping droplets were deposited surface tension forces pulled impacting droplets towards those already on the surface, a phenomena known as drawback. A dimensionless drawback index, quantifying the extent of droplet displacement, was calculated from experimental measurements for different values of droplet overlap. At large overlaps droplets deposited in a line or square array coalesced to form a circular film. When the droplet center-to-center distance increased, leading to less interaction, long, thin lines and square sheets were formed. As overlap was further decreased lines and sheets became discontinuous. A simple model was developed to predict the conditions under which rupture occurred. The lowest droplet overlap ratio (defined as droplet overlap distance divided by droplet spread diameter) at which a continuous liquid film could be formed was ?=0.293. At large overlap ratios (?>0.6) droplets deposited in a square array formed a circular film. The minimum thickness of a continuous film formed by coalescence of droplets was shown to vary from 5% to 70% of the initial droplet diameter while increasing impact Weber and Reynolds number reduced the film thickness. PMID:24461848

Dalili, Alireza; Chandra, Sanjeev; Mostaghimi, Javad; Fan, H T Charles; Simmer, Joseph C

2014-03-15

102

WW: An isolated three-stranded antiparallel beta-sheet domain that unfolds and refolds reversibly; evidence for a structured hydrophobic cluster in urea and GdnHCl and a disordered thermal unfolded state.  

PubMed Central

The objective of this study was to evaluate the suitability of the WW domain as a desirable model system to understand the folding and stability of an isolated three-stranded antiparallel beta-sheet structure. The WW domain was subjected to thermal and chaotropic denaturation/reconstitution utilizing a variety of biophysical methods. This three-stranded sheet folds reversibly and cooperatively utilizing both urea and GdnHCl as denaturants; however, the denatured state retains structure in the form of a hydrophobic cluster involving at least one aromatic side chain. In contrast to chaotropic denaturation, thermal denaturation appears to be more complete and may be a two state process. The suitability of the WW domain for future studies aimed at understanding the kinetics and thermodynamics of antiparallel beta-sheet folding clearly emerges from this initial study. The most exciting and significant result in this manuscript is the finding that the chaotropic denatured state of WW has a hydrophobic cluster as discerned by near-UV CD evidence. The role that the denatured state plays in the folding and stability of a three-stranded beta-sheets, and its capacity for preventing aggregation may be particularly important and is the subject of ongoing studies. PMID:10211830

Koepf, E. K.; Petrassi, H. M.; Sudol, M.; Kelly, J. W.

1999-01-01

103

Differential effects of beta-adrenergic receptor blockade in the medial prefrontal cortex during aversive and incidental taste memory formation.  

PubMed

The medial prefrontal cortex (mPFC) is a brain area crucial for memory, attention, and decision making. Specifically, the noradrenergic system in this cortex is involved in aversive learning, as well as in the retrieval of these memories. Some evidence suggests that this area has an important role during taste memory, particularly during conditioned taste aversion (CTA), a model of aversive memory. Despite some previous evidence, there is scarce information about the role of adrenergic receptors in the mPFC during formation of aversive taste memory and appetitive/incidental taste memory. The goal of this research was to evaluate the role of mPFC beta-adrenergic receptors during CTA acquisition/consolidation or CTA retrieval, as well as during incidental taste memory formation using the model of latent inhibition of CTA. The results showed that infusions in the mPFC of the beta-adrenergic antagonist propranolol before CTA acquisition impaired both short- and long-term aversive taste memory formation, and also that propranolol infusions before the memory test impaired CTA retrieval. However, propranolol infusions before pre-exposure to the taste during the latent inhibition procedure had no effect on incidental taste memory acquisition or consolidation. These data indicate that beta-adrenergic receptors in the mPFC have different functions during taste memory formation: they have an important role during aversive taste association as well as during aversive retrieval but not during incidental taste memory formation. PMID:20435101

Reyes-López, J; Nuñez-Jaramillo, L; Morán-Guel, E; Miranda, M I

2010-08-11

104

A novel step in beta-tubulin folding is important for heterodimer formation in Saccharomyces cerevisiae.  

PubMed Central

Undimerized beta-tubulin is toxic in the yeast S. cerevisiae. It can arise if levels of beta-tubulin and alpha-tubulin are unbalanced or if the tubulin heterodimer dissociates. We are using the toxicity of beta-tubulin to understand early steps in microtubule morphogenesis. We find that deletion of PLP1 suppresses toxic beta-tubulin formed by disparate levels of alpha- and beta-tubulin. That suppression occurs either when alpha-tubulin is modestly underexpressed relative to beta-tubulin or when beta-tubulin is inducibly and strongly overexpressed. Plp1p does not affect tubulin expression. Instead, a significant proportion of the undimerized beta-tubulin in plp1Delta cells is less toxic than that in wild-type cells. It is also less able to combine with alpha-tubulin to form a heterodimer. As a result, plp1Delta cells have lower levels of heterodimer. Importantly, plp1Delta cells that also lack Pac10, a component of the GimC/PFD complex, are even less affected by free beta-tubulin. Our results suggest that Plp1p defines a novel early step in beta-tubulin folding. PMID:14573467

Lacefield, Soni; Solomon, Frank

2003-01-01

105

Correlation and emplacement of a large, zoned, discontinuously exposed ash flow sheet: The 40 Ar\\/ 39 Ar chronology, paleomagnetism, and petrology of the Pahranagat Formation, Nevada  

Microsoft Academic Search

Many single-cryslal 4oAr\\/3gAr ages and thermoremanent magnetization directions have resolved the problematic stratigraphic correlation of the laterally and vertically zoned rhyolite ash flow sheet of the Pahranagat Formation in the southern Great Basin. This outflow sheet was previously designated by four different stratigraphic names in different locations over its highly discontinuous exposure area of 33,000 kmz. We show that it

Myron G. Best; Eric H. Christiansen; Alan L. Deino; C. Sherman Grommé; David G. Tingeyl

1995-01-01

106

Stemness and transdifferentiation of adipose-derived stem cells using L-ascorbic acid 2-phosphate-induced cell sheet formation.  

PubMed

Cell sheet technology has emerged as an important tissue engineering approach. Adipose-derived stem cells (ASCs) have valuable applications in regenerative medicine, but their stemness and differentiation capabilities in the cell sheet format have not been well investigated. In this study, we found that l-ascorbate 2-phosphate (A2-P), a stable form of ascorbic acid, significantly enhanced ASC proliferation and induced ASC sheet fabrication in 7 days with abundant extracellular matrix deposition. Importantly, A2-P treatment significantly enhanced expression of pluripotent markers Sox-2, Oct-4 and Nanog, but treating ASCs with antioxidants other than A2-P revealed no stemness enhancement. Moreover, ASC treatment with A2-P and a collagen synthesis inhibitor, L-2-azetidine carboxylic acid or cis-4-hydroxy-d-proline, significantly inhibited the A2-P-enhanced expression of stemness markers. These findings demonstrated that A2-P enhances stemness of ASCs through collagen synthesis and cell sheet formation. We also showed that A2-P-stimulated collagen synthesis in ASCs may be mediated through ERK1/2 pathway. By culturing the ASC sheets in proper induction media, ASC transdifferentiation capabilities into neuron and hepatocyte-like cells were significantly enhanced after cell sheet formation, while adipogenic and osteogenic differentiation capacities were still maintained. Using a murine model of healing-impaired cutaneous wound, faster wound healing was noted in the group that received ASC sheet treatment, and we observed significantly more engrafted ASCs with evidence of differentiation toward endothelial and epidermal lineages in the cutaneous wound tissue. Therefore, A2-P-mediated ASC sheet formation enhanced ASC stemness and transdifferentiation capabilities, thereby representing a promising approach for applications in regenerative medicine. PMID:24462360

Yu, Jiashing; Tu, Yuan-Kun; Tang, Yueh-Bih; Cheng, Nai-Chen

2014-04-01

107

Triggering Deglaciations: A Potential Mechanism Based on Laurentide Ice Sheet Induced Freshwater Forcing Changes and North Pacific Deep Water Formation  

NASA Astrophysics Data System (ADS)

A key puzzle left in explaining the 100 thousand year glacial cycles of the late Pleistocene is to find a mechanism by which CO2 is released into the atmosphere, without which the full amplitude of the deglaciation cannot be explained. Several hypothesis focus on changes in deep water formation, either in the North Atlantic via meltwater forcing, or the Southern Ocean, via changes in the Westerly winds. Based on new radiocarbon and boron isotope data, we suggest an additional center of action in the Pacific, where the ocean could have switched from its present state with no deep water formation to a state with deep ocean convection during Heinrich Stadial 1. Here we investigate atmospheric mechanisms that could lead to a salinification of the Pacific, and thus promote deepwater formation, using an idealized atmospheric general circulation model (GCM) and several comprehensive coupled climate models. We find that the topography of the Laurentide Ice Sheet is particularly important in controlling precipitation and overall freshwater forcing of the North Pacific and North Atlantic. Based on these results, we suggest that a Heinrich event in a sufficiently cold period - where the high latitude freshwater forcing has already been reduced - can act as a trigger for deep water formation in the North Pacific based on ice topography induced atmospheric circulation changes and corresponding freshwater forcing changes. As this deep water formation change is likely to be associated with a release of CO2, this cold period Heinrich event could act as a trigger for deglaciations.

Rae, J. W.; Wills, R.; Eisenman, I.; Schneider, T.

2013-12-01

108

Folding and aggregation of TEM beta-lactamase: analogies with the formation of inclusion bodies in Escherichia coli.  

PubMed Central

The enzyme TEM beta-lactamase has been used as a model for understanding the pathway leading to formation of inclusion bodies in Escherichia coli. The equilibrium denaturation of TEM beta-lactamase revealed that an intermediate that has lost enzymatic activity, native protein fluorescence, and UV absorption, but retains 60% of the native circular dichroism signal, becomes populated at intermediate (1.0-1.4 M) concentrations of guanidium chloride (GdmCl). This species exhibits a large increase in bis-1-anilino-8-naphthalene sulfonic acid fluorescence, indicating the presence of exposed hydrophobic surfaces. When TEM beta-lactamase was unfolded in different initial concentrations of GdmCl and refolded to the same final conditions by dialysis a distinct minimum in the yield of active protein was observed for initial concentrations of GdmCl in the 1.0-1.5 M range. It was shown that the lower reactivation yield was solely due to the formation of noncovalently linked aggregates. We propose that the aggregation of TEM beta-lactamase involves the association of a compact state having partially exposed hydrophobic surfaces. This hypothesis is consistent with our recent findings that TEM beta-lactamase inclusion bodies contains extensive secondary structure (Przybycien TM, Dunn JP, Valax P, Georgiou G, 1994, Protein Eng 7:131-136). Finally, we have also shown that protein aggregation was enhanced at higher temperatures and in the presence of 5 mM dithiothreitol and was inhibited by the addition of sucrose. These conditions exert a similar effect on the formation of inclusion bodies in vivo. PMID:7703842

Georgiou, G.; Valax, P.; Ostermeier, M.; Horowitz, P. M.

1994-01-01

109

TGF-beta completely blocks the formation of small-cell colonies: effects of mito-inhibitory factors on the proliferation of primary cultured rat hepatocytes.  

PubMed

The proliferation of primary cultured rat hepatocytes was observed in serum-free modified DMEM supplemented with 10 mM nicotinamide and 10 ng/ml EGF. These proliferating cells were mainly mononucleate and formed small-cell colonies after 4 days of culture. In the present experiment primary cultured hepatocytes were treated with Activin A, IL-1 beta, IL-6, and TGF-beta, which have been shown to be inhibitors of the DNA synthesis of rat hepatocytes, to examine whether these four inhibitors could suppress the formation of small-cell colonies. The initial DNA synthesis of more than 50% of the cells was dose-dependently inhibited by all the factors and the strongest inhibition was demonstrated in the cells treated with TGF-beta. Although Activin A and IL-6 did not block the colony development when the agents were administered at 96 h, just before the time when the cells started to form colonies, TGF-beta and IL-1 beta could inhibit the colony formation completely and partially, respectively. Transient treatment (48-72 h) with TGF-beta was enough to suppress colony development, while Activin A and IL-6 did not block the formation of colonies. IL-1 beta partially suppressed this formation. However, continuous administration (48-144 h) of IL-beta as well as TGF-beta stimulated the detachment of the cells from dishes and the remaining hepatocytes failed to form colonies. In addition, only TGF-beta could inhibit the DNA synthesis of most small cells in the established colonies as well as that of relatively large hepatocytes. Neither Activin A, IL-1 beta nor IL-6 could inhibit the DNA synthesis of the small cells. Thus, only TGF-beta could completely inhibit both the DNA synthesis of any type of hepatocyte and the formation of small-cell colonies. PMID:7641299

Mitaka, T; Kojima, T; Norioka, K; Mochizuki, Y

1995-04-01

110

Pulmonary surfactant-associated polypeptide C in a mixed organic solvent transforms from a monomeric alpha-helical state into insoluble beta-sheet aggregates.  

PubMed Central

In the 35-residue pulmonary surfactant-associated lipopolypeptide C (SP-C), the stability of the valyl-rich alpha-helix comprising residues 9-34 has been monitored by circular dichroism, nuclear magnetic resonance, and Fourier transform infrared spectroscopy in both a mixed organic solvent and in phospholipid micelles. The alpha-helical form of SP-C observed in freshly prepared solutions in a mixed solvent of CHCl3/CH3OH/0.1 M HCl 32:64:5 (v/v/v) at 10 degrees C undergoes within a few days an irreversible transformation to an insoluble aggregate that contains beta-sheet secondary structure. Hydrogen exchange experiments revealed that this conformational transition proceeds through a transition state with an Eyring free activation enthalpy of about 100 kJ mol(-1), in which the polypeptide segment 9-27 largely retains a helical conformation. In dodecylphosphocholine micelles, the helical form of SP-C was maintained after seven weeks at 50 degrees C. The alpha-helical form of SP-C thus seems to be the thermodynamically most stable state in this micellar environment, whereas its presence in freshly prepared samples in the aforementioned mixed solvent is due to a high kinetic barrier for unfolding. These observations support a previously proposed pathway for in vivo synthesis of SP-C through proteolytic processing from a 21-kDa precursor protein. PMID:9865947

Szyperski, T.; Vandenbussche, G.; Curstedt, T.; Ruysschaert, J. M.; Wuthrich, K.; Johansson, J.

1998-01-01

111

From Boron Cluster to Two-Dimensional Boron Sheet on Cu(111) Surface: Growth Mechanism and Hole Formation  

PubMed Central

As attractive analogue of graphene, boron monolayers have been theoretically predicted. However, due to electron deficiency of boron atom, synthesizing boron monolayer is very challenging in experiments. Using first-principles calculations, we explore stability and growth mechanism of various boron sheets on Cu(111) substrate. The monotonic decrease of formation energy of boron cluster BN with increasing cluster size and low diffusion barrier for a single B atom on Cu(111) surface ensure continuous growth of two-dimensional (2D) boron cluster. During growth process, hexagonal holes can easily arise at the edge of a 2D triangular boron cluster and then diffuse entad. Hence, large-scale boron monolayer with mixed hexagonal-triangular geometry can be obtained via either depositing boron atoms directly on Cu(111) surface or soft landing of small planar BN clusters. Our theoretical predictions would stimulate further experiments of synthesizing boron sheets on metal substrates and thus enrich the variety of 2D monolayer materials. PMID:24241341

Liu, Hongsheng; Gao, Junfeng; Zhao, Jijun

2013-01-01

112

From boron cluster to two-dimensional boron sheet on Cu(111) surface: growth mechanism and hole formation.  

PubMed

As attractive analogue of graphene, boron monolayers have been theoretically predicted. However, due to electron deficiency of boron atom, synthesizing boron monolayer is very challenging in experiments. Using first-principles calculations, we explore stability and growth mechanism of various boron sheets on Cu(111) substrate. The monotonic decrease of formation energy of boron cluster B(N) with increasing cluster size and low diffusion barrier for a single B atom on Cu(111) surface ensure continuous growth of two-dimensional (2D) boron cluster. During growth process, hexagonal holes can easily arise at the edge of a 2D triangular boron cluster and then diffuse entad. Hence, large-scale boron monolayer with mixed hexagonal-triangular geometry can be obtained via either depositing boron atoms directly on Cu(111) surface or soft landing of small planar BN clusters. Our theoretical predictions would stimulate further experiments of synthesizing boron sheets on metal substrates and thus enrich the variety of 2D monolayer materials. PMID:24241341

Liu, Hongsheng; Gao, Junfeng; Zhao, Jijun

2013-01-01

113

Lactate adversely affects the in vitro formation of endothelial cell tubular structures through the action of TGF-{beta}1  

SciTech Connect

When lactate accumulation in a tumor microenvironment reaches an average concentration of 10-20 mM, it tends to reflect a high degree of malignancy. However, the hypothesis that tumor-derived lactate has a number of partially adverse biological effects on malignant and tumor-associated host cells requires further evidence. The present study attempted to evaluate the impact of lactate on the process of angiogenesis, in particular on the formation of tubular structures. The endothelial cell (EC) network in desmoplastic breast tumors is primarily located in areas of reactive fibroblastic stroma. We employed a fibroblast-endothelial cell co-culture model as in vitro angiogenesis system normally producing florid in vitro tubule formation to analyze this situation. In contrast to previous studies, we found that lactate significantly reduces EC network formation in a dose-dependent manner as quantified by semi-automated morphometric analyses following immunohistochemical staining. The decrease in CD31-positive tubular structures and the number of intersections was independent of VEGF supplementation and became more pronounced in the presence of protons. The number of cells, primarily of the fibroblast population, was reduced but cell loss could not be attributed to a decrease in proliferative activity or pronounced apoptotic cell death. Treatment with 10 mM lactate was accompanied by enhanced mRNA expression and release of TGF-{beta}1, which also shows anti-angiogenic activity in the model. Both TGF-{beta}1 and lactate induced myofibroblastic differentiation adjacent to the EC tubular structures. The lactate response on the EC network was diminished by TGF-{beta}1 neutralization, indicating a causal relationship between lactate and TGF-{beta}1 in the finely tuned processes of vessel formation and maturation which may also occur in vivo within tumor tissue.

Schmid, Stephan A. [Institute of Pathology, University of Regensburg, 93042 Regensburg (Germany)]. E-mail: leoni.kunz-schughart@oncoray.de; Gaumann, Andreas [Institute of Pathology, University of Regensburg, 93042 Regensburg (Germany); Wondrak, Marit [Institute of Pathology, University of Regensburg, 93042 Regensburg (Germany); OncoRay-Center for Radiation Research in Oncology, Faculty of Medicine Carl Gustav Carus, TU Dresden, 01307 Dresden (Germany); Eckermann, Christoph [Institute of Pathology, University of Regensburg, 93042 Regensburg (Germany); Schulte, Stephanie [Institute of Pathology, Brigham and Women's Hospital, Boston, MA 02115 (United States); Mueller-Klieser, Wolfgang [Institute of Physiology and Pathophysiology, University of Mainz, 55128 Mainz (Germany); Wheatley, Denys N. [BioMedES, Leggat House, Keithhall, Inverrurie, Aberdeen, AB51 0LX (United Kingdom); Kunz-Schughart, Leoni A. [Institute of Pathology, University of Regensburg, 93042 Regensburg (Germany); OncoRay-Center for Radiation Research in Oncology, Faculty of Medicine Carl Gustav Carus, TU Dresden, 01307 Dresden (Germany)

2007-07-15

114

Thymosin Beta4 Regulates Cardiac Valve Formation Via Endothelial-Mesenchymal Transformation in Zebrafish Embryos  

PubMed Central

Thymosin beta4 (TB4) has multiple functions in cellular response in processes as diverse as embryonic organ development and the pathogeneses of disease, especially those associated with cardiac coronary vessels. However, the specific roles played by TB4 during heart valve development in vertebrates are largely unknown. Here, we identified a novel function of TB4 in endothelialmesenchymal transformation (EMT) in cardiac valve endocardial cushions in zebrafish. The expressions of thymosin family members in developing zebrafish embryos were determined by whole mount in situ hybridization. Of the thymosin family members only zTB4 was expressed in the developing heart region. Cardiac valve development at 48 h post fertilization was defected in zebrafish TB4 (zTB4) morpholino-injected embryos (morphants). In zTB4 morphants, abnormal linear heart tube development was observed. The expressions of bone morphogenetic protein (BMP) 4, notch1b, and hyaluronic acid synthase (HAS) 2 genes were also markedly reduced in atrio-ventricular canal (AVC). Endocardial cells in the AVC region were stained with anti-Zn5 antibody reactive against Dm-grasp (an EMT marker) to observe EMT in developing cardiac valves in zTB4 morphants. EMT marker expression in valve endothelial cells was confirmed after transfection with TB4 siRNA in the presence of transforming growth factor ? (TGF?) by RT-PCR and immunofluorescent assay. Zn5-positive endocardial AVC cells were not observed in zTB4 morphants, and knockdown of TB4 suppressed TGF-?-induced EMT in ovine valve endothelial cells. Taken together, our results demonstrate that TB4 plays a pivotal role in cardiac valve formation by increasing EMT. PMID:24732964

Shin, Sun-Hye; Lee, Sangkyu; Bae, Jong-Sup; Jee, Jun-Goo; Cha, Hee-Jae; Lee, You Mie

2014-01-01

115

Chemistry Reference Sheets  

NSDL National Science Digital Library

This reference sheet, presented by the National Nanotechnology Infrastructure Network provides a valuable chemistry reference sheet for high school students. Definition of terms, diagrams, abbreviations, mathematical notations, the periodic table, and other useful information is provided in an easy to use format. Included in this lesson are the front and back sides of this reference sheet.

2014-07-25

116

Physical Science Reference Sheets  

NSDL National Science Digital Library

This reference sheet, presented by the National Nanotechnology Infrastructure Network provides a valuable physical science reference sheet for high school students. Definition of terms, diagrams, abbreviations, mathematical notations, the periodic table, and other useful information is provided in an easy to use format. Included in this lesson are the front and back sides of this reference sheet.

2014-07-11

117

Efficient 3'-end formation of human beta-globin mRNA in vivo requires sequences within the last intron but occurs independently of the splicing reaction.  

PubMed

The second intron (betaIVS-II) of the human beta-globin gene is essential for the accumulation of stable cytoplasmic mRNA and is implicated in promoting efficient 3'-end formation. This report presents quantitative comparisons between betaIVS-II mutants at physiological levels of expression from within a natural chromatin context in vivo which further defines it's function. In marked contrast to a beta-globin gene lacking a second intron, two mutants defective in splicing (small size or a splice donor mutation), still undergo essentially normal levels of 3'-end formation and in the absence of exon skipping. Therefore, 3' cleavage of beta-globin transcripts requires the presence of betaIVS-II sequences, but not the splicing reaction. The placement of betaIVS-II in the IVS-I position did not reduce the efficiency of 3' cleavage indicating that the distance between the necessary element(s) in this intron and the polyadenylation recognition site is not a crucial factor. Subsequent placement of betaIVS-I in the intron II position, reduced the efficiency of 3'-end formation to only 16% of normal. A direct replacement of intron II by the heterologous introns betaIVS-I or alpha-globin IVS-II, only partially substitute (16 and 30% respectively) for betaIVS-II. Hybrid introns show that efficient 3'-end formation is strongly enhanced by the presence of the terminal 60 nt of betaIVS-II. These data imply that the last intervening sequence of multiple intron containing genes is a principal determinant of the efficiency of 3'-end formation and may act as a post-transcriptional regulatory step in gene expression. PMID:9443963

Antoniou, M; Geraghty, F; Hurst, J; Grosveld, F

1998-02-01

118

Efficient 3'-end formation of human beta-globin mRNA in vivo requires sequences within the last intron but occurs independently of the splicing reaction.  

PubMed Central

The second intron (betaIVS-II) of the human beta-globin gene is essential for the accumulation of stable cytoplasmic mRNA and is implicated in promoting efficient 3'-end formation. This report presents quantitative comparisons between betaIVS-II mutants at physiological levels of expression from within a natural chromatin context in vivo which further defines it's function. In marked contrast to a beta-globin gene lacking a second intron, two mutants defective in splicing (small size or a splice donor mutation), still undergo essentially normal levels of 3'-end formation and in the absence of exon skipping. Therefore, 3' cleavage of beta-globin transcripts requires the presence of betaIVS-II sequences, but not the splicing reaction. The placement of betaIVS-II in the IVS-I position did not reduce the efficiency of 3' cleavage indicating that the distance between the necessary element(s) in this intron and the polyadenylation recognition site is not a crucial factor. Subsequent placement of betaIVS-I in the intron II position, reduced the efficiency of 3'-end formation to only 16% of normal. A direct replacement of intron II by the heterologous introns betaIVS-I or alpha-globin IVS-II, only partially substitute (16 and 30% respectively) for betaIVS-II. Hybrid introns show that efficient 3'-end formation is strongly enhanced by the presence of the terminal 60 nt of betaIVS-II. These data imply that the last intervening sequence of multiple intron containing genes is a principal determinant of the efficiency of 3'-end formation and may act as a post-transcriptional regulatory step in gene expression. PMID:9443963

Antoniou, M; Geraghty, F; Hurst, J; Grosveld, F

1998-01-01

119

Functional analysis of the beta and epsilon lycopene cyclase enzymes of Arabidopsis reveals a mechanism for control of cyclic carotenoid formation.  

PubMed Central

Carotenoids with cyclic end groups are essential components of the photosynthetic membranes in all plants, algae, and cyanobacteria. These lipid-soluble compounds protect against photooxidation, harvest light for photosynthesis, and dissipate excess light energy absorbed by the antenna pigments. The cyclization of lycopene (psi, psi-carotene) is a key branch point in the pathway of carotenoid biosynthesis. Two types of cyclic end groups are found in higher plant carotenoids: the beta and epsilon rings. Carotenoids with two beta rings are ubiquitous, and those with one beta and one epsilon ring are common; however, carotenoids with two epsilon rings are rare. We have identified and sequenced cDNAs that encode the enzymes catalyzing the formation of these two rings in Arabidopsis. These beta and epsilon cyclases are encoded by related, single-copy genes, and both enzymes use the linear, symmetrical lycopene as a substrate. However, the epsilon cyclase adds only one ring, forming the monocyclic delta-carotene (epsilon, psi-carotene), whereas the beta cyclase introduces a ring at both ends of lycopene to form the bicyclic beta-carotene (beta, beta-carotene). When combined, the beta and epsilon cyclases convert lycopene to alpha-carotene (beta, epsilon-carotene), a carotenoid with one beta and one epsilon ring. The inability of the epsilon cyclase to catalyze the introduction of a second epsilon ring reveals the mechanism by which production and proportions of beta,beta- and beta, epsilon-carotenoids may be controlled and adjusted in plants and algae, while avoiding the formation of the inappropriate epsilon,epsilon-carotenoids. PMID:8837512

Cunningham, F X; Pogson, B; Sun, Z; McDonald, K A; DellaPenna, D; Gantt, E

1996-01-01

120

On the formation of the tunnel valleys of the southern Laurentide ice sheet  

USGS Publications Warehouse

Catastrophic releases of meltwater, produced by basal melting and stored for decades in subglacial reservoirs at high pressure, may have been responsible for eroding the broad, deep tunnel valleys that are common along the margins of some lobes of the southern Laurentide ice sheet. We surmise that these releases began when the high water pressure was transmitted to the margin through the substrate. The water pressure in the substrate at the margin would then have been significantly above the overburden pressure, leading to sapping failure. Headward erosion of a conduit in the substrate (piping) could then tap the stored water, resulting in the outburst. In some situations, development of a siphon may have lowered the reservoir below its overflow level, thus tapping additional water. Following the flood, the seal could have reformed and the reservoir refilled, setting up conditions for another outburst. Order of magnitude calculations suggest that once emptied, a subglacial reservoir could refill in a matter of decades. The amount of water released during several outbursts appears to be sufficient to erode a tunnel valley. We think that tunnel valleys are most likely to have formed in this way where and when the glacier margin was frozen to the bed and permafrost extended from the glacier forefield several kilometers back under the glacier, as reservoirs would then have been larger and more common, and the seal more robust and more likely to reform after an outburst. ?? 2006 Elsevier Ltd. All rights reserved.

Hooke, R. LeB; Jennings, C.E.

2006-01-01

121

A simplified vortex sheet roll-up method for formation flight  

E-print Network

This thesis studies the influence of the roll-up of a wake on the benefits in induced drag and rolling moment experienced by a close formation of two elliptically loaded wings. The roll-up of the leading wake is computed ...

Denis, Amandine, 1981-

2004-01-01

122

On Non-Equilibrium and Current Sheet Formation in Line-Tied Mag... http://flux.aps.org/meetings/YR9596/BAPSDPP96/abs/S660010.html 1 of 1 3/10/05 11:16 AM  

E-print Network

conditions. It follows that if such a static equilibrium is driven unstable by footpoint motionsOn Non-Equilibrium and Current Sheet Formation in Line-Tied Mag... http - Concourse Level, Adam's Mark [8S.10] On Non-Equilibrium and Current Sheet Formation in Line-Tied Magnetic

Ng, Chung-Sang

123

Global Simulations of Differentially Rotating Magnetized Disks: Formation of Low-beta Filaments and Structured Coronae.  

PubMed

We present the results of three-dimensional global magnetohydrodynamic simulations of the Parker-shearing instability in a differentially rotating torus initially threaded by toroidal magnetic fields. An equilibrium model of a magnetized torus is adopted as an initial condition. When beta0=Pgas&solm0;Pmag approximately 1 at the initial state, magnetic flux buoyantly escapes from the disk and creates looplike structures similar to those in the solar corona. Inside the torus, the growth of nonaxisymmetric magnetorotational (or Balbus & Hawley) instability generates magnetic turbulence. Magnetic field lines are tangled on a small scale, but on a large scale they show low azimuthal wavenumber spiral structure. After several rotation periods, the system oscillates around a state with beta approximately 5. We found that magnetic pressure-dominated (beta<1) filaments are created in the torus. The volume filling factor of the region in which betabeta regions may lead to violent flaring activities in accretion disks and in galactic gas disks. PMID:10702134

Machida; Hayashi; Matsumoto

2000-03-20

124

Formation of a long-lived hot field reversed configuration by dynamically merging two colliding high-{beta} compact toroids  

SciTech Connect

A high temperature field reversed configuration (FRC) has been produced in the newly built, world's largest compact toroid (CT) facility, C-2, by colliding and merging two high-{beta} CTs produced using the advanced field-reversed {theta}-pinch technology. This long-lived, stable merged state exhibits the following key properties: (1) apparent increase in the poloidal flux from the first pass to the final merged state, (2) significantly improved confinement compared to conventional {theta}-pinch FRCs with flux decay rates approaching classical values in some cases, (3) strong conversion from kinetic energy into thermal energy with total temperature (T{sub e} + T{sub i}) exceeding 0.5 keV, predominantly into the ion channel. Detailed modeling using a new 2-D resistive magnetohydrodynamic (MHD) code, LamyRidge, has demonstrated, for the first time, the formation, translation, and merging/reconnection dynamics of such extremely high-{beta} plasmas.

Guo, H. Y.; Binderbauer, M. W.; Barnes, D.; Putvinski, S.; Rostoker, N.; Sevier, L.; Tuszewski, M.; Anderson, M. G.; Andow, R.; Bonelli, L.; Brown, R.; Bui, D. Q.; Bystritskii, V.; Clary, R.; Cheung, A. H.; Conroy, K. D.; Deng, B. H.; Dettrick, S. A.; Douglass, J. D.; Feng, P. [Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, California 92688 (United States)

2011-05-15

125

The geologic mapping of Venus using C-1 format: Sheets 75N254, 60N263  

NASA Technical Reports Server (NTRS)

The results of geologic mapping of Venus, produced on the base of Magellan images, are presented. We submit two C-1 format geologic maps with the appropriate legend. The mapping territory was taken from Venera 15 and 16 missions and geologic maps were composed. Magellan images allow us to divide some types of the plains units to determine the lava flow direction and to map with better accuracy.

Shalimov, I. V.

1992-01-01

126

Formation of Ni–Cu–Platinum Group Element sulfide mineralization in the Sudbury Impact Melt Sheet  

Microsoft Academic Search

Summary The Ni–Cu–Platinum Group Element (PGE) sulfide deposits of the Sudbury Structure have provided a major portion of the world’s total nickel production and their host rocks have been the subject of numerous research studies, yet a number of perplexing problems remain to be solved. On the one hand, studies seeking to explain the formation of the Sudbury Structure have

R. R. Keays; P. C. Lightfoot

2004-01-01

127

Does Long-Term Administration of a Beta-Blocker (Timolol) Induce Fibril-Based Cataract Formation In-vivo?  

PubMed Central

Timolol is a non-selective beta-adrenergic receptor antagonist administered for treating glaucoma, heart attacks and hypertension. In the present study, we set out to determine whether or not timolol can provoke cataract formation, thus the influence of timolol on the amyloid-type aggregation of crystallin was investigated. We then provided experimental evidence of crystallin aggregation and its induction by timolol using different spectroscopic measurements. Turbidimetric measurements as well as ThT fluorescence data indicated that timolol induce extent of crystallin amyloid formation. The kinetic of protein aggregation was also changed in presence of increasing concentrations of the drug suggesting that long-term drug administration may contribute to the development of cataract. Since the consequence of timolol-crystallin interaction has yet to be identified, additional data on it may help us to postpone amyloid cataract formation.

Nikbakht, Mohammad Reza; Ashrafi-Kooshk, Mohammad Reza; Jaafari, Morteza; Ghasemi, Moosa; Khodarahmi, Reza

2014-01-01

128

Interdendritic Strain and Macrosegregation-Coupled Phenomena for Interdendritic Crack Formation in Direct-Chill Cast Sheet Ingots  

NASA Astrophysics Data System (ADS)

In a study of the early stages of dendritic solidification in the direct-chill cast sheet ingots, the coupled effect of interdendritic strain and macrosegregation on the interdendritic cracks formation in dendritic equiaxed structure has been investigated by the metallographic study of ingot samples and by performing a set of mathematical analyses for AA-6061 and AA-1050 aluminum alloys. The metallographic investigation contains microstructure examinations and macrosegregation measurements of collected samples from plant trials. The mathematical analysis consists of a two-dimensional (2-D) fluid flow, heat flow, interdendritic strain, and macrosegregation-coupled model. Also, a simple approach to measure interdendritic crack has been developed based on the accumulative interdendritic strain criterion, local dendritic phases, and the crystal distortion correlation factor resulting from steep positive local segregation. The model predications have clarified the effect of high positive macrosegregation on the surface and subsurface interdendritic crack formation. It has been revealed that interdendritic strain starts to generate just below the liquidus temperature, resulting from shrinkage of liquid?solid phase transformation and contraction of dendritic solid in the incoherent mushy region. In this region, the coupled effect of the shrinkage/contraction mechanism increases the interdendritic distances between equiaxed crystals and the interdendritic crack begins to nucleate. Subsequently, in the coherent mushy region, the different interdendritic strain sources start to affect significantly the distances between equiaxed crystals in a diverse way, and therefore, the final morphology of interdendritic crack begins to form. The mechanism of interdendritic crack formation during dendritic equiaxed structure solidification and the possible solutions to this problem are discussed.

EL-Bealy, Mostafa Omar

2012-06-01

129

Separation of drug stereoisomers by the formation of. beta. -cyclodextrin inclusion complexes  

Microsoft Academic Search

For many drugs, only racemic mixtures are available for clinical use. Because different stereoisomers of drugs often cause different physiological responses, the use of pure isomers could elicit more exact therapeutic effects. Differential complexation of a variety of drug stereoisomers by immobilized ..beta..-cyclodextrin was investigated. Chiral recognition and racemic resolution were observed with a number of compounds from such clinically

D. W. Armstrong; T. J. Ward; R. D. Armstrong; T. E. Beesley

1986-01-01

130

Separation of Drug Stereoisomers by the Formation of beta Cyclodextrin Inclusion Complexes  

Microsoft Academic Search

For many drugs, only racemic mixtures are available for clinical use. Because different stereoisomers of drugs often cause different physiological responses, the use of pure isomers could elicit more exact therapeutic effects. Differential complexation of a variety of drug stereoisomers by immobilized beta -cyclodextrin was investigated. Chiral recognition and racemic resolution were observed with a number of compounds from such

Daniel W. Armstrong; Timothy J. Ward; R. Douglas Armstrong; Thomas E. Beesley

1986-01-01

131

Mucous sheet production by poritid corals  

Microsoft Academic Search

Mucous sheets, produced by poritid corals, provided a test system to determine the contribution of mucus production to reef trophodynamics. This dissertation examined mucous sheet formation by two common Caribbean poritids, Porites astreoides and Porites furcata.Mucous sheet formation by both P. furcata and P. astreoides had a lunar periodicity with the timing of mucous sheet formation distinct for each species.

Mary Alice Coffroth

1988-01-01

132

Predicted alpha-helix/beta-sheet secondary structures for the zinc-binding motifs of human papillomavirus E7 and E6 proteins by consensus prediction averaging and spectroscopic studies of E7.  

PubMed Central

The E7 and E6 proteins are the main oncoproteins of human papillomavirus types 16 and 18 (HPV-16 and HPV-18), and possess unknown protein structures. E7 interacts with the cellular tumour-suppressor protein pRB and contains a zinc-binding site with two Cys-Xaa2-Cys motifs spaced 29 or 30 residues apart. E6 interacts with another cellular tumour-suppressor protein p53 and contains two zinc-binding sites, each with two Cys-Xaa2-Cys motifs at a similar spacing of 29 or 30 residues. By using the GOR I/III, Chou-Fasman, SAPIENS and PHD methods, the effectiveness of consensus secondary structure predictions on zinc-finger proteins was first tested with sequences for 160 transcription factors and 72 nuclear hormone receptors. These contain Cys2His2 and Cys2Cys2 zinc-binding regions respectively, and possess known atomic structures. Despite the zinc- and DNA-binding properties of these protein folds, the major alpha-helix structures in both zinc-binding regions were correctly identified. Thus validated, the use of these prediction methods with 47 E7 sequences indicated four well-defined alpha-helix (alpha) and beta-sheet (beta) secondary structure elements in the order beta beta alpha beta in the zinc-binding region of E7 at its C-terminus. The prediction was tested by Fourier transform infrared spectroscopy of recombinant HPV-16 E7 in H2O and 2H2O buffers. Quantitative integration showed that E7 contained similar amounts of alpha-helix and beta-sheet structures, in good agreement with the averaged prediction of alpha-helix and beta-sheet structures in E7 and also with previous circular dichroism studies. Protein fold recognition analyses predicted that the structure of the zinc-binding region in E7 was similar to a beta beta alpha beta motif found in the structure of Protein G. This is consistent with the E7 structure predictions, despite the low sequence similarities with E7. This predicted motif is able to position four Cys residues in proximity to a zinc atom. A model for the zinc-binding motif of E7 was constructed by combining the Protein G coordinates with those for the zinc-binding site in transcription factor TFIIS. Similar analyses for the two zinc-binding motifs in E6 showed that they have different alpha/beta secondary structures from that in E7. When compared with 12 other zinc-binding proteins, these results show that E7 and E6 are predicted to possess novel types of zinc-binding structure. PMID:8870673

Ullman, C G; Haris, P I; Galloway, D A; Emery, V C; Perkins, S J

1996-01-01

133

alpha 2-macroglobulin Associates with beta -amyloid Peptide and Prevents Fibril Formation  

Microsoft Academic Search

We have used the yeast two-hybrid system to isolate cDNAs encoding proteins that specifically interact with the 42-aa beta -amyloid peptide (Abeta ), a major constituent of senile plaques in Alzheimer's disease. The carboxy terminus of alpha 2-macroglobulin (alpha 2M), a proteinase inhibitor released in response to inflammatory stimuli, was identified as a strong and specific interactor of Abeta ,

Stephen R. Hughes; Olga Khorkova; Shefali Goyal; Joerg Knaeblein; Jeffrey Heroux; Norbert G. Riedel; Sudhir Sahasrabudhe

1998-01-01

134

Synthetic peptides corresponding to human follicle-stimulating hormone (hFSH)-beta-(1-15) and hFSH-beta-(51-65) induce uptake of 45Ca++ by liposomes: evidence for calcium-conducting transmembrane channel formation  

SciTech Connect

We have previously described FSH receptor-mediated influx of 45Ca++ in cultured Sertoli cells from immature rats and receptor-enriched proteoliposomes via activation of voltage-sensitive and voltage-independent calcium channels. We have further shown that this effect of FSH does not require cholera toxin- or pertussis toxin-sensitive guanine nucleotide binding protein or activation of adenylate cyclase. In the present study, we have identified regions of human FSH-beta-subunit which appear to be involved in mediating calcium influx. We screened 11 overlapping peptide amides representing the entire primary structure of hFSH-beta-subunit for their effects on 45Ca++ flux in FSH receptor-enriched proteoliposomes. hFSH-beta-(1-15) and hFSH-beta-(51-65) induced uptake of 45Ca++ in a concentration-related manner. This effect of hFSH-beta-(1-15) and hFSH-beta-(51-65) was also observed in liposomes lacking incorporated FSH receptor. Reducing membrane fluidity by incubating liposomes (containing no receptor) with hFSH-beta-(1-15) or hFSH-beta-(51-65) at temperatures lower than the transition temperatures of their constituent phospholipids resulted in no significant (P greater than 0.05) difference in 45Ca++ uptake. The effectiveness of the calcium ionophore A23187, however, was abolished. Ruthenium red, a voltage-independent calcium channel antagonist, was able to completely block uptake of 45Ca++ induced by hFSH-beta-(1-15) and hFSH-beta-(51-65) whereas nifedipine, a calcium channel blocker specific for L-type voltage-sensitive calcium channels, was without effect. These results suggest that in addition to its effect on voltage-sensitive calcium channel activity, interaction of FSH with its receptor may induce formation of transmembrane aqueous channels which also facilitate influx of extracellular calcium.

Grasso, P.; Santa-Coloma, T.A.; Reichert, L.E. Jr. (Department of Biochemistry, Albany Medical College, New York, NY (USA))

1991-06-01

135

Ion mobility–mass spectrometry reveals a conformational conversion from random assembly to ?-sheet in amyloid fibril formation  

Microsoft Academic Search

Amyloid cascades that lead to peptide ?-sheet fibrils and plaques are central to many important diseases. Recently, intermediate assemblies of these cascades were identified as the toxic agents that interact with cellular machinery. The location and cause of the transformation from a natively unstructured assembly to the ?-sheet oligomers found in all fibrils is important in understanding disease onset and

Christian Bleiholder; Nicholas F. Dupuis; Thomas Wyttenbach; Michael T. Bowers

2010-01-01

136

Thermal conditions at the bed of the Laurentide ice sheet in Maine during deglaciation: implications for esker formation  

Microsoft Academic Search

The University of Maine Ice Sheet Model was used to study basal conditions during retreat of the Laurentide ice sheet in Maine. Within 150 km of the margin, basal melt rates average ˜5 mm a-1 during retreat. They decline over the next 100 km, so areas of frozen bed develop in northern Maine during retreat. By integrating the melt rate

Roger Leb. Hooke; James Fastook

2007-01-01

137

Spontaneous Formation of Oligomers and Fibrils in Large-Scale Molecular Dynamics Simulations of A-beta Peptides  

NASA Astrophysics Data System (ADS)

Protein aggregation is associated with serious and eventually-fatal neurodegenerative diseases including Alzheimer's and Parkinson's. While atomic resolution molecular dynamics simulations have been useful in this regard, they are limited to examination of either oligomer formation by a small number of peptides or analysis of the stability of a moderate number of peptides placed in trial or known experimental structures. We describe large scale intermediate-resolution molecular dynamics simulations of the spontaneous formation of fibrils by systems containing large numbers ( 48) of peptides including A-beta (16-22), and A-beta ( 17-42) peptides. We trace out the aggregation process from an initial configuration of random coils to proto-filaments with cross-? structures and demonstrate how kinetics dictates the structural details of the fully formed fibril. Fibrillization kinetics depends strongly on the temperature. Nucleation and templated growth via monomer addition occur at and near a transition temperature above which fibrils are unlikely to form. Oligomeric merging and structural rearrangement are observed at lower temperatures.

Hall, Carol

2013-03-01

138

Astrocyte transforming growth factor beta 1 promotes inhibitory synapse formation via CaM kinase II signaling.  

PubMed

The balance between excitatory and inhibitory synaptic inputs is critical for the control of brain function. Astrocytes play important role in the development and maintenance of neuronal circuitry. Whereas astrocytes-derived molecules involved in excitatory synapses are recognized, molecules and molecular mechanisms underlying astrocyte-induced inhibitory synapses remain unknown. Here, we identified transforming growth factor beta 1 (TGF-?1), derived from human and murine astrocytes, as regulator of inhibitory synapse in vitro and in vivo. Conditioned media derived from human and murine astrocytes induce inhibitory synapse formation in cerebral cortex neurons, an event inhibited by pharmacologic and genetic manipulation of the TGF-? pathway. TGF-?1-induction of inhibitory synapse depends on glutamatergic activity and activation of CaM kinase II, which thus induces localization and cluster formation of the synaptic adhesion protein, Neuroligin 2, in inhibitory postsynaptic terminals. Additionally, intraventricular injection of TGF-?1 enhanced inhibitory synapse number in the cerebral cortex. Our results identify TGF-?1/CaMKII pathway as a novel molecular mechanism underlying astrocyte control of inhibitory synapse formation. We propose here that the balance between excitatory and inhibitory inputs might be provided by astrocyte signals, at least partly achieved via TGF-?1 downstream pathways. Our work contributes to the understanding of the GABAergic synapse formation and may be of relevance to further the current knowledge on the mechanisms underlying the development of various neurological disorders, which commonly involve impairment of inhibitory synapse transmission. GLIA 2014;62:1917-1931. PMID:25042347

Diniz, Luan Pereira; Tortelli, Vanessa; Garcia, Matheus Nunes; Araújo, Ana Paula Bérgamo; Melo, Helen M; Seixas da Silva, Gisele S; De Felice, Fernanda G; Alves-Leon, Soniza Vieira; de Souza, Jorge Marcondes; Romão, Luciana Ferreira; Castro, Newton Gonçalves; Gomes, Flávia Carvalho Alcantara

2014-12-01

139

Esker formation and meltwater routing on and beneath the margins of the last Cordilleran Ice Sheet: implications for modelling ice sheet hydrology  

NASA Astrophysics Data System (ADS)

It has been suggested that ice sheet drainage system organization (i.e. channelized or distributed) may be predicted from variables such as substrate character (rigidity, permeability) and ice surface slope. Analysis of esker systems from paleoglacial environments is instructive in testing the validity of such model predictions. We combine data from grids of ground penetrating radar (GPR) and electrical resistivity (ER) with sedimentological observations, water well data and detailed geomorphic investigation to infer esker genesis and describe the character and context of three eskers at the margins of the last Cordilleran Ice Sheet (CIS) on British Columbia's (BC's) southern Fraser Plateau. This region is characterized by soft (deformation and deformed lodgement tills), low permeability diamictons (~50% clay and silt content) overlying basalt. Esker systems on the plateau include: 1) a 12 km long, relatively straight (sinuosity ratio, Sr, 1.061), single thread esker (Green Lake esker), with both undulatory and flat-topped sections, deposited in a 38 km long subglacial erosional corridor; 2) a 4.5 km long single thread, undulating, and moderately sinuous esker (Hooke Road esker, Sr 1.36) in the vicinity of ice marginal channels (useful in determining ice surface slope); and 3) a 6 km long esker-like ridge (Young Lake esker), that transitions from flat-topped upflow to undulating downflow and is bordered by closed depressions on the floor of a glacially-modified gorge. The individual eskers are respectively interpreted as: 1) a subglacial esker formed during supraglacial lake drainage, under low ice surface slopes; 2) a supraglacial esker formed by drainage across the ice marginal zone; and 3) an esker-like ridge formed in an ice-walled, unroofed channel within disintegrating ice blocks at a point beyond the intact ice margin. Together these landforms suggest that: 1) supraglacial water was a significant component of water flow at the base of the CIS; 2) CIS decay was, at times, facilitated by high magnitude water flows; and 3) organization of channelized drainage systems was probably not limited to rigid, impermeable beds or to locations of high ice surface slopes. Our data indicate that emerging models of ice sheet hydrology should incorporate sources of unsteady supraglacial drainage.

Perkins, A. J.; Brennand, T.; Burke, M. J.

2011-12-01

140

Beta- lactam antibiotics stimulate biofilm formation in non-typeable haemophilus influenzae by up-regulating carbohydrate metabolism.  

PubMed

Non-typeable Haemophilus influenzae (NTHi) is a common acute otitis media pathogen, with an incidence that is increased by previous antibiotic treatment. NTHi is also an emerging causative agent of other chronic infections in humans, some linked to morbidity, and all of which impose substantial treatment costs. In this study we explore the possibility that antibiotic exposure may stimulate biofilm formation by NTHi bacteria. We discovered that sub-inhibitory concentrations of beta-lactam antibiotic (i.e., amounts that partially inhibit bacterial growth) stimulated the biofilm-forming ability of NTHi strains, an effect that was strain and antibiotic dependent. When exposed to sub-inhibitory concentrations of beta-lactam antibiotics NTHi strains produced tightly packed biofilms with decreased numbers of culturable bacteria but increased biomass. The ratio of protein per unit weight of biofilm decreased as a result of antibiotic exposure. Antibiotic-stimulated biofilms had altered ultrastructure, and genes involved in glycogen production and transporter function were up regulated in response to antibiotic exposure. Down-regulated genes were linked to multiple metabolic processes but not those involved in stress response. Antibiotic-stimulated biofilm bacteria were more resistant to a lethal dose (10 µg/mL) of cefuroxime. Our results suggest that beta-lactam antibiotic exposure may act as a signaling molecule that promotes transformation into the biofilm phenotype. Loss of viable bacteria, increase in biofilm biomass and decreased protein production coupled with a concomitant up-regulation of genes involved with glycogen production might result in a biofilm of sessile, metabolically inactive bacteria sustained by stored glycogen. These biofilms may protect surviving bacteria from subsequent antibiotic challenges, and act as a reservoir of viable bacteria once antibiotic exposure has ended. PMID:25007395

Wu, Siva; Li, Xiaojin; Gunawardana, Manjula; Maguire, Kathleen; Guerrero-Given, Debbie; Schaudinn, Christoph; Wang, Charles; Baum, Marc M; Webster, Paul

2014-01-01

141

Beta- Lactam Antibiotics Stimulate Biofilm Formation in Non-Typeable Haemophilus influenzae by Up-Regulating Carbohydrate Metabolism  

PubMed Central

Non-typeable Haemophilus influenzae (NTHi) is a common acute otitis media pathogen, with an incidence that is increased by previous antibiotic treatment. NTHi is also an emerging causative agent of other chronic infections in humans, some linked to morbidity, and all of which impose substantial treatment costs. In this study we explore the possibility that antibiotic exposure may stimulate biofilm formation by NTHi bacteria. We discovered that sub-inhibitory concentrations of beta-lactam antibiotic (i.e., amounts that partially inhibit bacterial growth) stimulated the biofilm-forming ability of NTHi strains, an effect that was strain and antibiotic dependent. When exposed to sub-inhibitory concentrations of beta-lactam antibiotics NTHi strains produced tightly packed biofilms with decreased numbers of culturable bacteria but increased biomass. The ratio of protein per unit weight of biofilm decreased as a result of antibiotic exposure. Antibiotic-stimulated biofilms had altered ultrastructure, and genes involved in glycogen production and transporter function were up regulated in response to antibiotic exposure. Down-regulated genes were linked to multiple metabolic processes but not those involved in stress response. Antibiotic-stimulated biofilm bacteria were more resistant to a lethal dose (10 µg/mL) of cefuroxime. Our results suggest that beta-lactam antibiotic exposure may act as a signaling molecule that promotes transformation into the biofilm phenotype. Loss of viable bacteria, increase in biofilm biomass and decreased protein production coupled with a concomitant up-regulation of genes involved with glycogen production might result in a biofilm of sessile, metabolically inactive bacteria sustained by stored glycogen. These biofilms may protect surviving bacteria from subsequent antibiotic challenges, and act as a reservoir of viable bacteria once antibiotic exposure has ended. PMID:25007395

Wu, Siva; Li, Xiaojin; Gunawardana, Manjula; Maguire, Kathleen; Guerrero-Given, Debbie; Schaudinn, Christoph; Wang, Charles; Baum, Marc M.; Webster, Paul

2014-01-01

142

Sedimentologic evidence for outburst floods from the Laurentide Ice Sheet margin in Wisconsin, USA: implications for tunnel-channel formation  

Microsoft Academic Search

Clast-supported boulder gravel in outwash-fans along the glacial-maximum margin of the Laurentide Ice Sheet in Wisconsin indicates the occurrence of outburst floods. These sediments, with clast intermediate axes of up to 2m, are located downstream of tunnel channels and were deposited shortly before cessation of glaciofluvial activity on each fan. Since tunnel channels with fans are widespread along the ice-sheet

Paul M. Cutler; Patrick M. Colgan; David M. Mickelson

2002-01-01

143

Mitochondrial DNA damage in a mouse model of Alzheimer's disease decreases amyloid beta plaque formation  

PubMed Central

Mitochondrial DNA (mtDNA) damage and the generation of reactive oxygen species have been associated with and implicated in the development and progression of Alzheimer's disease. To study how mtDNA damage affects reactive oxygen species and amyloid beta (A?) pathology in vivo, we generated an Alzheimer's disease mouse model expressing an inducible mitochondrial-targeted endonuclease (Mito-PstI) in the central nervous system. Mito-PstI cleaves mtDNA causing mostly an mtDNA depletion, which leads to a partial oxidative phosphorylation defect when expressed during a short period in adulthood. We found that a mild mitochondrial dysfunction in adult neurons did not exacerbate A? accumulation and decreased plaque pathology. Mito-PstI expression altered the cleavage pathway of amyloid precursor protein without increasing oxidative stress in the brain. These data suggest that mtDNA damage is not a primary cause of Ab accumulation. PMID:23702344

Fukui, Hirokazu; Moraes, Carlos T.

2014-01-01

144

Cysteine conjugate beta-lyase activity of rat erythrocytes and formation of beta-lyase-derived globin monoadducts and cross-links after in vitro exposure of erythrocytes to S-(1,2-dichlorovinyl)-L-cysteine.  

PubMed

S-(1,2-Dichlorovinyl)-L-cysteine (DCVC), a mutagenic and nephrotoxic metabolite of trichloroethylene, can be bioactivated to reactive metabolites, S-(1,2-dichlorovinyl)-L-cysteine sulfoxide (DCVCS) or chlorothioketene and/or 2-chlorothionoacetyl chloride, by cysteine conjugate S-oxidase (S-oxidase) and cysteine conjugate beta-lyase (beta-lyase), respectively. Previously, we characterized the reactivity of DCVCS with Hb upon incubation of erythrocytes with DCVCS and provided evidence for the formation of distinct DCVCS-Hb monoadducts and cross-links in both isolated erythrocytes and rats given DCVCS. In the present study, we investigated DCVC bioactivation and Hb adduct formation in isolated rat erythrocytes incubated with DCVC (9 and 450 microM) at 37 degrees C and pH 7.4. The results suggested that no DCVCS monoadducts or cross-links were formed; however, LC/electrospray ionization/MS and matrix-assisted laser desorption/ionization/MS of trypsin-digested globin peptides revealed the presence of beta-lyase-derived globin monoadducts and cross-links. Adducts and cross-links in which the sulfur atom of the reactive sulfur intermediates were replaced by oxygen have also been detected. Use of SDS-PAGE provided additional evidence for globin cross-link formation in the presence of DCVC. Interestingly, the MS results suggest that the observed peptide selectivity of the beta-lyase-derived reactive sulfur/oxygen-containing species was different than that previously observed with DCVCS. While these results suggested that erythrocytes have beta-lyase but not S-oxidase activity, further support for this hypothesis was obtained using S-(2-benzothiazolyl)-L-cysteine, an alternative substrate for beta-lyases. Collectively, the results demonstrate the utility of Hb adducts and cross-links to characterize the metabolic pathway responsible for DCVC bioactivation in erythrocytes and to provide distinct biomarkers for each reactive metabolite. PMID:19572755

Barshteyn, Nella; Elfarra, Adnan A

2009-07-01

145

Biology Reference Sheets  

NSDL National Science Digital Library

This reference sheet, presented by the National Nanotechnology Infrastructure Network provides a valuable list biology reference material for high school students in the life sciences. Definition of terms, diagrams, abbreviations, mathematical notations, and other useful information is provided in an easy to use format. Included in this lesson are the front and back sides of this reference sheet.

2014-07-25

146

Diverse effects of beta-tubulin mutations on microtubule formation and function  

PubMed Central

We have used in vitro mutagenesis and gene replacement to construct five new cold-sensitive mutations in TUB2, the sole gene encoding beta- tubulin in the yeast Saccharomyces cerevisiae. These and one previously isolated tub2 mutant display diverse phenotypes that have allowed us to define the functions of yeast microtubules in vivo. At the restrictive temperature, all of the tub2 mutations inhibit chromosome segregation and block the mitotic cell cycle. However, different microtubule arrays are present in these arrested cells depending on the tub2 allele. One mutant (tub2-401) contains no detectable microtubules, two (tub2-403 and tub2-405) contain greatly diminished levels of both nuclear and cytoplasmic microtubules, one (tub2-104) contains predominantly nuclear microtubules, one (tub2-402) contains predominantly cytoplasmic microtubules, and one (tub2-404) contains prominent nuclear and cytoplasmic microtubule arrays. Using these mutants we demonstrate here that cytoplasmic microtubules are necessary for nuclear migration during the mitotic cell cycle and for nuclear migration and fusion during conjugation; only those mutants that possess cytoplasmic microtubules are able to perform these functions. We also show that microtubules are not required for secretory vesicle transport in yeast; bud growth and invertase secretion occur in cells which contain no microtubules. PMID:3290223

1988-01-01

147

Increased estrogen receptor beta expression correlates with decreased spine formation in the rat hippocampus.  

PubMed

Estrogens play an important role in the brain function acting through two receptor types, ERalpha and ERbeta, both well-recognized as transcription factors. In this study, we investigated the ERbeta mRNA and protein levels in the rat hippocampus by using two in vivo models that are known to affect synapse formation. Natural estrous-proestrous cycle was used as a model in which a marked decrease in the density of hippocampal synapses was previously observed between proestrus and estrus. We have found that ERbeta mRNA and protein were displayed in high levels in the estrus and in low levels in the proestrous phase. By applying kainic acid (KA) to adult rats, we demonstrated that up-regulation of ERbeta mRNA and protein in hippocampal CA regions was vulnerable to KA-induced excitotoxicity. Furthermore, we note a concomitant decrease of ERbeta in the excitotoxicity-resistant denate gyrus that undergoes intense plastic changes, including synaptogenesis. These data suggested that decreases in ERbeta expression correlated with increase in synapse formation. This notion has been tested in vitro in hippocampal cultures, in which overexpression of ERbeta by means of gene transfection resulted in the lowering of the dendritic spine density that was elevated by estrogen. In summary, our results suggest that ERbeta inhibits synapse formation in hippocampal neurons. PMID:16526034

Szymczak, Sylwia; Kalita, Katarzyna; Jaworski, Jacek; Mioduszewska, Basia; Savonenko, Alena; Markowska, Alicja; Merchenthaler, Istvan; Kaczmarek, Leszek

2006-01-01

148

Natalizumab plus interferon beta-1a reduces lesion formation in relapsing multiple sclerosis.  

PubMed

The SENTINEL study showed that the addition of natalizumab improved outcomes for patients with relapsing multiple sclerosis (MS) who had experienced disease activity while receiving interferon beta-1a (IFNbeta-1a) alone. Previously unreported secondary and tertiary magnetic resonance imaging (MRI) measures are presented here. Patients received natalizumab 300 mg (n=589) or placebo (n=582) intravenously every 4 weeks plus IFNbeta-1a 30 microg intramuscularly once weekly. Annual MRI scans allowed comparison of a range of MRI end points versus baseline. Over 2 years, 67% of patients receiving natalizumab plus IFNbeta-1a remained free of new or enlarging T2-lesions compared with 30% of patients receiving IFNbeta-1a alone. The mean change from baseline in T2 lesion volume over 2 years decreased in patients receiving natalizumab plus IFNbeta-1a and increased in those receiving IFNbeta-1a alone (-277.5mm(3) versus 525.6mm(3); p<0.001). Compared with IFNbeta-1a alone, add-on natalizumab therapy resulted in a smaller increase in mean T1-hypointense lesion volume after 2 years (1821.3mm(3) versus 2210.5mm(3); p<0.001), a smaller mean number of new T1-hypointense lesions over 2 years (2.3 versus 4.1; p<0.001), and a slower rate of brain atrophy during the second year of therapy (-0.31% versus -0.40%; p=0.020). Natalizumab add-on therapy reduced gadolinium-enhancing, T1-hypointense, and T2 MRI lesion activity and slowed brain atrophy progression in patients with relapsing MS who experienced disease activity despite treatment with IFNbeta-1a alone. PMID:20236661

Radue, Ernst-Wilhelm; Stuart, William H; Calabresi, Peter A; Confavreux, Christian; Galetta, Steven L; Rudick, Richard A; Lublin, Fred D; Weinstock-Guttman, Bianca; Wynn, Daniel R; Fisher, Elizabeth; Papadopoulou, Athina; Lynn, Frances; Panzara, Michael A; Sandrock, Alfred W

2010-05-15

149

Non-redundant roles of phosphoinositide 3-kinase isoforms alpha and beta in glycoprotein VI-induced platelet signaling and thrombus formation.  

PubMed

Platelets are activated by adhesion to vascular collagen via the immunoglobulin receptor, glycoprotein VI (GPVI). This causes potent signaling toward activation of phospholipase Cgamma2, which bears similarity to the signaling pathway evoked by T- and B-cell receptors. Phosphoinositide 3-kinase (PI3K) plays an important role in collagen-induced platelet activation, because this activity modulates the autocrine effects of secreted ADP. Here, we identified the PI3K isoforms directly downstream of GPVI in human and mouse platelets and determined their role in GPVI-dependent thrombus formation. The targeting of platelet PI3Kalpha or -beta strongly and selectively suppressed GPVI-induced Ca(2+) mobilization and inositol 1,4,5-triphosphate production, thus demonstrating enhancement of phospholipase Cgamma2 by PI3Kalpha/beta. That PI3Kalpha and -beta have a non-redundant function in GPVI-induced platelet activation and thrombus formation was concluded from measurements of: (i) serine phosphorylation of Akt, (ii) dense granule secretion, (iii) intracellular Ca(2+) increases and surface expression of phosphatidylserine under flow, and (iv) thrombus formation, under conditions where PI3Kalpha/beta was blocked or p85alpha was deficient. In contrast, GPVI-induced platelet activation was insensitive to inhibition or deficiency of PI3Kdelta or -gamma. Furthermore, PI3Kalpha/beta, but not PI3Kgamma, contributed to GPVI-induced Rap1b activation and, surprisingly, also to Rap1b-independent platelet activation via GPVI. Together, these findings demonstrate that both PI3Kalpha and -beta isoforms are required for full GPVI-dependent platelet Ca(2+) signaling and thrombus formation, partly independently of Rap1b. This provides a new mechanistic explanation for the anti-thrombotic effect of PI3K inhibition and makes PI3Kalpha an interesting new target for anti-platelet therapy. PMID:19815551

Gilio, Karen; Munnix, Imke C A; Mangin, Pierre; Cosemans, Judith M E M; Feijge, Marion A H; van der Meijden, Paola E J; Olieslagers, Servé; Chrzanowska-Wodnicka, Magdalena B; Lillian, Rivka; Schoenwaelder, Simone; Koyasu, Shigeo; Sage, Stewart O; Jackson, Shaun P; Heemskerk, Johan W M

2009-12-01

150

Highly sensitive and selective spectrofluorimetric determination of tolnaftate through the formation of ternary inclusion complex of beta-naphthol/beta-cyclodextrin/anionic surfactant system.  

PubMed

An indirect spectrofluorimetric method with high sensitivity and selectivity was developed for the determination of antifungal drug: tolnaftate (TNF), depending on the supramolecular multi-recognition interaction among the anionic surfactant sodium laurylsulfate (SLS), beta-cyclodextrin (beta-CD) and beta-naphthol (ROH). The mechanism of the inclusion was studied and discussed by means of fluorescence spectrum, infra-red spectrograms and (1)HNMR spectroscopy. Results showed that the naphthalene ring of ROH and the hydrophobic hydrocarbon chain of SLS were included into the beta-CD's cavity to form a ROH:SLS:beta-CD ternary inclusion complex with stoichiometry of 1:1:1 at room temperature, which provided effective protection for the excited state of ROH. At lambda(ex)/lambda(em)=273/360 nm, the fluorescence intensity was linear over a tolnaftate concentration range of 2.46 x 10(-9) to 2.10 x 10(-6)mol L(-1). The detection limit and relative standard deviation was 7.50 x 10(-10)mol L(-1) and 1.4%, respectively. The interference of 31 foreign substances was slight. The proposed method had been successfully applied to the determination of tolnaftate in artificial mixed samples with almost quantitative recovery. PMID:18970541

Tang, Bo; Wang, Xu; Wang, Guangli; Yu, Chengguang; Chen, Zhenzhen

2006-03-15

151

Evidence for adduct formation at the semiconductor-solution interface. Photoluminescent properties of cadmium selenide in the presence of lanthanide. beta. -diketonate complexes  

SciTech Connect

Photoluminescence (PL) measurements of etched, single-crystal n-CdSe demonstrate that the semiconductor surface engages in adduct formation with a family of lanthanide {beta}-diketonate complexes, Ln(fod){sub 3} (Ln = lanthanide; fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato anion), in isooctane ambient.

Murphy, C.J.; Ellis, A.B. (Univ. of Wisconsin, Madison (USA))

1990-04-05

152

Nanospace-confined formation of flattened Sn sheets in pre-seeded graphenes for lithium ion batteries  

NASA Astrophysics Data System (ADS)

Flattened Sn sheets are prepared from the pre-seeded Sn salt in the interlayer nanospace of a graphene membrane, which acts as a template to shape Sn crystals and prevent the aggregation. The sandwich structure clamping Sn sheets accommodates the volume change during charge/discharge. We show that the hybrid possesses excellent rate performance and cycling stability as an anode for lithium ion batteries.Flattened Sn sheets are prepared from the pre-seeded Sn salt in the interlayer nanospace of a graphene membrane, which acts as a template to shape Sn crystals and prevent the aggregation. The sandwich structure clamping Sn sheets accommodates the volume change during charge/discharge. We show that the hybrid possesses excellent rate performance and cycling stability as an anode for lithium ion batteries. Electronic supplementary information (ESI) available: Details of the preparation and characterization of G/Sn-F, G/Sn-L and G/Sn-S. See DOI: 10.1039/c4nr01924e

Li, Zhengjie; Lv, Wei; Zhang, Chen; Qin, Jiwen; Wei, Wei; Shao, Jiao-Jing; Wang, Da-Wei; Li, Baohua; Kang, Feiyu; Yang, Quan-Hong

2014-07-01

153

Mucous sheet formation on poritid corals: An evaluation of coral mucus as a nutrient source on reefs  

Microsoft Academic Search

The production, release, and subsequent consumption of coral mucus on reefs has been portrayed as a potential pathway for the transfer of coral and zooxanthellae production to other reef organisms. However, reported mucus production rates and analyses of nutritional value vary widely. Poritid corals provide a test system to measure mucus production because they produce mucous sheets which can be

M. A. Coffroth

1990-01-01

154

TGF-{beta} signals the formation of a unique NF1/Smad4-dependent transcription repressor-complex in human diploid fibroblasts  

SciTech Connect

Highlights: {yields} TGF-{beta} induces the formation of unique nuclear NF1/Smad4 complexes that repress expression of the ANT-2 gene. {yields} Repression is mediated through an NF1-dependent repressor element in the promoter. {yields} The formation of NF1/Smad4 complexes and the repression of ANT2 are prevented by inhibitors of p38 kinase and TGF-{beta} RI. {yields} NF1/Smad complexes implicate novel role for NF1 and Smad proteins in the regulation of growth. -- Abstract: We earlier reported the formation of a unique nuclear NF1/Smad complex in serum-restricted fibroblasts that acts as an NF1-dependent repressor of the human adenine nucleotide translocase-2 gene (ANT2) [K. Luciakova, G. Kollarovic, P. Barath, B.D. Nelson, Growth-dependent repression of human adenine nucleotide translocator-2 (ANT2) transcription: evidence for the participation of Smad and Sp family proteins in the NF1-dependent repressor complex, Biochem. J. 412 (2008) 123-130]. In the present study, we show that TGF-{beta}, like serum-restriction: (a) induces the formation of NF1/Smad repressor complexes, (b) increases binding of the complexes to the repressor elements (Go elements) in the ANT2 promoter, and (c) inhibits ANT2 expression. Repression of ANT2 by TGF-{beta} is eliminated by mutating the NF1 binding sites in the Go repressor elements. All of the above responses to TGF-{beta} are prevented by inhibitors of TGF-{beta} RI and MAPK p38. These inhibitors also prevent NF1/Smad4 repressor complex formation and repression of ANT2 expression in serum-restricted cells, suggesting that similar signaling pathways are initiated by TGF-{beta} and serum-restriction. The present finding that NF1/Smad4 repressor complexes are formed through TGF-{beta} signaling pathways suggests a new, but much broader, role for these complexes in the initiation or maintenance of the growth-inhibited state.

Luciakova, Katarina, E-mail: katarina.luciakova@savba.sk [Cancer Research Institute, Slovak Academy of Sciences, Bratislava, Vlarska 7, 833 91 Bratislava (Slovakia)] [Cancer Research Institute, Slovak Academy of Sciences, Bratislava, Vlarska 7, 833 91 Bratislava (Slovakia); Kollarovic, Gabriel; Kretova, Miroslava; Sabova, Ludmila [Cancer Research Institute, Slovak Academy of Sciences, Bratislava, Vlarska 7, 833 91 Bratislava (Slovakia)] [Cancer Research Institute, Slovak Academy of Sciences, Bratislava, Vlarska 7, 833 91 Bratislava (Slovakia); Nelson, B. Dean [Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91 Stockholm (Sweden)] [Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91 Stockholm (Sweden)

2011-08-05

155

Exploring the Influence of Carbon Nanoparticles on the Formation of ?-Sheet-Rich Oligomers of IAPP22–28 Peptide by Molecular Dynamics Simulation  

PubMed Central

Recent advances in nanotechnologies have led to wide use of nanomaterials in biomedical field. However, nanoparticles are found to interfere with protein misfolding and aggregation associated with many human diseases. It is still a controversial issue whether nanoparticles inhibit or promote protein aggregation. In this study, we used molecular dynamics simulations to explore the effects of three kinds of carbon nanomaterials including graphene, carbon nanotube and C60 on the aggregation behavior of islet amyloid polypeptide fragment 22–28 (IAPP22–28). The diverse behaviors of IAPP22–28 peptides on the surfaces of carbon nanomaterials were studied. The results suggest these nanomaterials can prevent ?-sheet formation in differing degrees and further affect the aggregation of IAPP22–28. The ?–? stacking and hydrophobic interactions are different in the interactions between peptides and different nanoparticles. The subtle differences in the interaction are due to the difference in surface curvature and area. The results demonstrate the adsorption interaction has competitive advantages over the interactions between peptides. Therefore, the fibrillation of IAPP22–28 may be inhibited at its early stage by graphene or SWCNT. Our study can not only enhance the understanding about potential effects of nanomaterials to amyloid formation, but also provide valuable information to develop potential ?-sheet formation inhibitors against type II diabetes. PMID:23755253

Guo, Jingjing; Li, Jiazhong; Zhang, Yan; Jin, Xiaojie; Liu, Huanxiang; Yao, Xiaojun

2013-01-01

156

DEFECT PROPERTIES IN beta-SiC UNDER IRRADIATION-FORMATION ENERGY OF INTERSTITIAL CLUSTERS  

SciTech Connect

Molecular dynamics and molecular statics calculations have been performed to evaluate the formation energy of self-interstitial atom (SIA) clusters in -SiC. For SIA-clusters with stoichiometric composition, an attempt has been made to fit the calculated data points to a polynomial function of cluster size n. The resultant equation EF=1.01n1+2.04n1/2 may indicate the applicability to a wide range of cluster sizes. This formalization will be useful for the development of accurate model on nucleation and growth of SIA-clusters, which is required for the modeling on irradiation-induced microstructural evolutions of materials in nuclear fusion reactors.

Watanabe, Y.; Morishita, K.; Kohyama, Akira; Heinisch, Howard L.; Gao, Fei

2009-07-01

157

Architectural variability of confined turbidite sheet-sands: facies, geometry and infill of associated elementary channels. Examples from the Trois Evêchés Basin, Annot Sandstone Formation, SE France  

NASA Astrophysics Data System (ADS)

The worldwide known Annot Sandstone Formation has been considered as a reference of confined siliciclastic turbidite system. This formation crops out in SE France and represents the Upper Eocene to Lower Oligocene gravitary infill of complex foreland basins, developed in front of the Alpine thrusts. This system can be assimilated as a sand-rich turbidite ramp, sourced by multiple fan deltas leading to topographically complex sub-basins. Highly bypassing channelized systems dominate in the most proximal and most confined areas. They distally evolve to relatively less confined areas, in which sedimentary bodies appear to be more continuous and homogenous on a regional scale. These last architectural elements, defined as sheet-sands or depositional lobes, have been the focus of this study in poorly documented areas. From an important dataset made of very high resolution outcrop correlations (gathered mainly in the Trois Evêchés and Lauzanier sub-basins), we have quantified the complex distribution of sedimentary facies and structures, grain-size and key surfaces in sand-rich sheets. This was done to understand their variability from depositional event to architectural element scales and to better characterize dimensions and characteristics of their components. Six main types of architectural elements were defined, composed of both channelized and unchannelized elements. Channelized units show a high variability in terms of facies, geometry and patterns of infill that are related to multiple erosional and depositional processes, which will be discussed. We notably relate some evidences of sinuous channels, represented by lateral accretion deposits in the channel complex axis and by low angle cross-bedded facies. We interpret this particular facies as the result of flow deconfinement and overbanks above channel margins. The stratigraphic analysis of elementary objects allows us to propose a genetic model and a spatial distribution model of sheet-sand architectural elements. The latter provides their longitudinal repartition, from proximal vertically stacked internal channels to distal compensating sheets. Those features have not been accurately described in relatively distal sand-rich turbidite deposits so far and this high internal variability necessarily implies heterogeneities both in terms of petrophysical characteristics and reservoir connection. Besides, it also implies reconsidering sedimentary processes involved in these environments. Key Words: Annot Sandstones, Confined Systems, Reservoir Heterogeneities, Turbidite Sheet-sands.

Etienne, S.; Mulder, T.; Pace, A.; Bez, M.; Desaubliaux, G.

2012-04-01

158

Ion mobility-mass spectrometry reveals a conformational conversion from random assembly to ?-sheet in amyloid fibril formation  

NASA Astrophysics Data System (ADS)

Amyloid cascades that lead to peptide ?-sheet fibrils and plaques are central to many important diseases. Recently, intermediate assemblies of these cascades were identified as the toxic agents that interact with cellular machinery. The location and cause of the transformation from a natively unstructured assembly to the ?-sheet oligomers found in all fibrils is important in understanding disease onset and the development of therapeutic agents. Largely, research on this early oligomeric region was unsuccessful because all the traditional techniques measure only the average oligomer properties of the ensemble. We utilized ion-mobility methods to deduce the peptide self-assembly mechanism and examined a series of amyloid-forming peptides clipped from larger peptides or proteins associated with disease. We provide unambiguous evidence for structural transitions in each of these fibril-forming peptide systems and establish the potential of this method for the development of therapeutic agents and drug evaluation.

Bleiholder, Christian; Dupuis, Nicholas F.; Wyttenbach, Thomas; Bowers, Michael T.

2011-02-01

159

Image formation by linear and nonlinear digital scanned light-sheet fluorescence microscopy with Gaussian and Bessel beam profiles  

PubMed Central

We present the implementation of a combined digital scanned light-sheet microscope (DSLM) able to work in the linear and nonlinear regimes under either Gaussian or Bessel beam excitation schemes. A complete characterization of the setup is performed and a comparison of the performance of each DSLM imaging modality is presented using in vivo Caenorhabditis elegans samples. We found that the use of Bessel beam nonlinear excitation results in better image contrast over a wider field of view. PMID:22808423

Olarte, Omar E.; Licea-Rodriguez, Jacob; Palero, Jonathan A.; Gualda, Emilio J.; Artigas, David; Mayer, Jurgen; Swoger, Jim; Sharpe, James; Rocha-Mendoza, Israel; Rangel-Rojo, Raul; Loza-Alvarez, Pablo

2012-01-01

160

On the formation of pre-onset azimuthal pressure gradient in the near-Earth plasma sheet  

NASA Astrophysics Data System (ADS)

Xing et al. (2011) demonstrated by case study that the plasma sheet pressure gradient at ˜11 REnear the substorm onset meridian undergoes a substantial duskward enhancement shortly before substorm onset as identified from the auroral poleward expansion. It was suggested that the increased upward FAC driven by this pressure gradient enhancement lead to the thin onset arc intensification from which the poleward expansion initiates. In the present study, we employ the multiTHEMIS spacecraft in azimuthal conjunction -at ˜-11 REand examine the ion flux and distributions during the period of pressure gradient enhancement, and identify two categories of events. For events with pressure gradient change ?2 min prior to onset, strong earthward ion flux enhancements covering the energy range from several keV to above 25 keV were observed by the spacecraft identifying the higher pressure increase, while at the same time the ion distributions show a substantial earthward shift in velocity space. These resemble the ion acceleration ahead of earthward moving dipolarization fronts. On the other hand, the spacecraft observing the lower pressure increase found weaker or no ion flux enhancements and had nearly isotropic distributions, indicating that longitudinally localized dipolarization fronts are responsible for the pressure gradient development. These pressure gradient enhancements were in the duskward (dawnward) direction for measurements to the east (west) of the onset region. For pressure gradient enhancement >2 min prior to onset, stronger plasma sheet thinning was observed by the spacecraft identifying the larger pressure increase and the ion distributions appear nearly isotropic, which suggests plasma redistribution in the undisturbed plasma sheet. These two categories suggest that both dipolarization fronts and growth phase plasma sheet localized thinning can drive azimuthal pressure gradient enhancement near the onset meridian and cause pre-onset thin auroral arc intensification, though the dipolarization front events appear to be substantially more common based on our 14 events.

Xing, X.; Lyons, L. R.; Zhou, X.-Z.; Angelopoulos, V.; Donovan, E.; Larson, D.; Carlson, C.; Auster, U.

2012-08-01

161

Copper induces increased beta-sheet content in the scrapie-susceptible ovine prion protein PrPVRQ compared with the resistant allelic variant PrPARR.  

PubMed Central

Prion diseases are characterized by conformational change in the copper-binding protein PrP (prion protein). Polymorphisms in ovine PrP at amino acid residues 136, 154 and 171 are associated with variation in susceptibility to scrapie. PrPVRQ [PrP(Val136/Arg154/Gln171)] or PrPARQ [PrP(Ala136/Arg154/Gln171)] animals show susceptibility to scrapie, whereas those that express Ala136/Arg154/Arg171 (PrPARR) show resistance. Results are presented here that show PrPVRQ and PrPARR display different conformational responses to metal-ion interaction. At 37 degrees C copper induced different levels of b-sheet content in the allelic variants of ovine full-length prion protein (amino acid 25-232). PrPVRQ showed a significant increase in b-sheet content when exposed to copper at 37 degrees C, whereas PrPARR remained relatively unchanged. The conversion of a-helical PrPVRQ to b-sheet form was shown by CD spectroscopy and the decreased binding of C-terminal specific monoclonal anti-PrP antibodies. This conversion to an increased b-sheet form did not occur with truncated PrPVRQ (amino acids 89-233), which demonstrates that additional metal-binding sites outside of the N-terminus may not overtly influence the overall structure of ovine PrP. Despite the difference in b-sheet content, both the scrapie-susceptible and -resistant allelic forms of ovine PrP acquired resistance to proteinase K digestion following exposure to copper at 37 degrees C, suggesting the potential for disease-associated PrPARR to accumulate in vivo. Our present study demonstrates that allelic variants of ovine PrP differ in their structure and response to the interaction with copper. These observations will contribute to a better understanding of the mechanism of susceptibility and resistance to prion disease. PMID:14969585

Wong, Edmond; Thackray, Alana M; Bujdoso, Raymond

2004-01-01

162

Removal of the N-terminal hexapeptide from human beta2-microglobulin facilitates protein aggregation and fibril formation.  

PubMed Central

The solution structure and stability of N-terminally truncated beta2-microglobulin (deltaN6beta2-m), the major modification in ex vivo fibrils, have been investigated by a variety of biophysical techniques. The results show that deltaN6beta2-m has a free energy of stabilization that is reduced by 2.5 kcal/mol compared to the intact protein. Hydrogen exchange of a mixture of the truncated and full-length proteins at microM concentrations at pH 6.5 monitored by electrospray mass spectrometry reveals that deltaN6beta2-m is significantly less protected than its wild-type counterpart. Analysis of deltaN6beta2-m by NMR shows that this loss of protection occurs in beta strands I, III, and part of II. At mM concentration gel filtration analysis shows that deltaN6beta2-m forms a series of oligomers, including trimers and tetramers, and NMR analysis indicates that strand V is involved in intermolecular interactions that stabilize this association. The truncated species of beta2-microglobulin was found to have a higher tendency to self-associate than the intact molecule, and unlike wild-type protein, is able to form amyloid fibrils at physiological pH. Limited proteolysis experiments and analysis by mass spectrometry support the conformational modifications identified by NMR and suggest that deltaN6beta2-m could be a key intermediate of a proteolytic pathway of beta2-microglobulin. Overall, the data suggest that removal of the six residues from the N-terminus of beta2-microglobulin has a major effect on the stability of the overall fold. Part of the tertiary structure is preserved substantially by the disulfide bridge between Cys25 and Cys80, but the pairing between beta-strands far removed from this constrain is greatly perturbed. PMID:10850793

Esposito, G.; Michelutti, R.; Verdone, G.; Viglino, P.; Hernández, H.; Robinson, C. V.; Amoresano, A.; Dal Piaz, F.; Monti, M.; Pucci, P.; Mangione, P.; Stoppini, M.; Merlini, G.; Ferri, G.; Bellotti, V.

2000-01-01

163

Intrastriatal injection of interleukin-1 beta triggers the formation of neuromyelitis optica-like lesions in NMO-IgG seropositive rats  

PubMed Central

Background Neuromyelitis optica (NMO) is a severe, disabling disease of the central nervous system (CNS) characterized by the formation of astrocyte-destructive, neutrophil-dominated inflammatory lesions in the spinal cord and optic nerves. These lesions are initiated by the binding of pathogenic aquaporin 4 (AQP4)-specific autoantibodies to astrocytes and subsequent complement-mediated lysis of these cells. Typically, these lesions form in a setting of CNS inflammation, where the blood–brain barrier is open for the entry of antibodies and complement. However, it remained unclear to which extent pro-inflammatory cytokines and chemokines contribute to the formation of NMO lesions. To specifically address this question, we injected the cytokines interleukin-1 beta, tumor necrosis factor alpha, interleukin-6, interferon gamma and the chemokine CXCL2 into the striatum of NMO-IgG seropositive rats and analyzed the tissue 24 hours later by immunohistochemistry. Results All injected cytokines and chemokines led to profound leakage of immunoglobulins into the injected hemisphere, but only interleukin-1 beta induced the formation of perivascular, neutrophil-infiltrated lesions with AQP4 loss and complement-mediated astrocyte destruction distant from the needle tract. Treatment of rat brain endothelial cells with interleukin-1 beta, but not with any other cytokine or chemokine applied at the same concentration and over the same period of time, caused profound upregulation of granulocyte-recruiting and supporting molecules. Injection of interleukin-1 beta caused higher numbers of blood vessels with perivascular, cellular C1q reactivity than any other cytokine tested. Finally, the screening of a large sample of CNS lesions from NMO and multiple sclerosis patients revealed large numbers of interleukin-1 beta-reactive macrophages/activated microglial cells in active NMO lesions but not in MS lesions with comparable lesion activity and location. Conclusions Our data strongly suggest that interleukin-1 beta released in NMO lesions and interleukin-1 beta-induced production/accumulation of complement factors (like C1q) facilitate neutrophil entry and BBB breakdown in the vicinity of NMO lesions, and might thus be an important secondary factor for lesion formation, possibly by paving the ground for rapid lesion growth and amplified immune cell recruitment to this site. PMID:24252536

2013-01-01

164

Metabolism of prostaglandin D2 in isolated rat lung: the stereospecific formation of 9 alpha,11 beta-prostaglandin F2 from prostaglandin D2.  

PubMed

The metabolic transformation of exogenous prostaglandin D2 was investigated in isolated perfused rat lung. Dose-dependent formation (2-150 ng) of 9 alpha,11 beta-prostaglandin F2, corresponding to about 0.1% of the perfused dose of prostaglandin D2, was observed by specific radioimmunoassay both in the perfusate and in lung tissue after a 5-min perfusion. To investigate the reason for this low conversion ratio, we analyzed the metabolites of tritium-labeled 9 alpha,11 beta-prostaglandin F2 and prostaglandin D2 by boric acid-impregnated TLC and HPLC. By 5 min after the start of perfusion, 9 alpha,11 beta-prostaglandin F2 disappeared completely from the perfusate and the major product formed remained unchanged during the remainder of the 30-min perfusion. The major product was separated by TLC and identified as 13,14-dihydro-15-keto-9 alpha,11 beta-prostaglandin F2 by GC/MS. In contrast, pulmonary breakdown of prostaglandin D2 was slow and two major metabolites in the perfusate increased with time, each representing 56% and 11% of the total radioactivity at the end of the perfusion. The major product (56%) was identified as 13,14-dihydro-15-ketoprostaglandin D2 and the minor one (11%) was tentatively identified as 13,14-dihydro-15-keto-9 alpha,11 beta-prostaglandin F2 based on the results from radioimmunoassays, TLC, HPLC, and the time course of pulmonary breakdown. These results demonstrate that the metabolism of prostaglandin D2 in rat lung involves at least two pathways, one by 15-hydroxyprostaglandin dehydrogenase and the other by 11-ketoreductase, and that the 9 alpha,11 beta-prostaglandin F2 formed is rapidly metabolized to 13,14-dihydro-15-keto-9 alpha,11 beta-prostaglandin F2. PMID:3467796

Hayashi, H; Ito, S; Watanabe, K; Negishi, M; Shintani, T; Hayaishi, O

1987-02-23

165

Double Mantle Plume Upwelling—A Possible Formation Mechanism of Beta Plateau and Devana Chasma,Venus  

NASA Astrophysics Data System (ADS)

Ning Ding,Zuoxun Zeng,China University of Geosciences,Wuhan,430074,China NingDing.eagle@gmail.com Introduction:Venus represents a‘one plate planet’[1],and the uplift,fractures and volcanism in Beta Regio on Venus are considered to be formed by lithosphere uplift driven by a hot plume[2]. Based on the double peaking saddle landform,we suggest the tectonic pattern of double mantle plume upwelling to interpret the formation mechanism of Beta Plateau and Devana Chasma.We take a physical modeling to validate this possibility. Model:There is no ductile shear in Venus[3],so we use quartz sands to simulate the crust of Venus.We use two wood stickes 1.5cm in diameter rising from the rubber canvas slowly and straight till about half of the model,then falling down slowly and straight.The base is a hard rubber plate,in the center of which,there are two holes 3cm in diameter,and the distance between them is 5cm.The holes are covered by rubber canvas.We use the quartz sands in colours of white, red and black with particle size of 70 mess as the model materials. Result:Fig.1:At the beginning of the wood stickes upwelling,only fine radial cracks are formed above the upwelling from central to outside.With the upwelling continue,surface energy of the fine radial cracks increase and make the cracks unstable,finally,the fine radial cracks connect each other and form a fracture zone.And then the two mantle plume downwelling,the fracture zone is developed to form a chasma at the end. Fig.2:The four profiles all form reverse faults outside and normal faults inside.But the difference is the faults in the middle of the chasma goes deeper than others.It is the pattern of Beta Plateau where the tectonic rising is cut by Devana Chasma zone in the topographic features. Fig.3:From the tow fig., we can see two points similar:a.the elevation is high and distribution area is large around the area of two upwelling and it is high around the area of chasma,but the distribution area is small;b.both of them shows saddle shape and two highland connectting bya chasma. Discussion:Based on the‘Geology Map of V-17’,two highlands of Northern part of Devana Chasma,but the material Unit of North and South highland are different.The material Units of North highland are the oldest unit tt and t,the material Unit of South highland is pl and the material Unit of rift is r are both the youngest unit.From the Magellan SAR mosaic[5],we can clearly see Devana Chasma cut the material Unit of tt and pl.So the two highlands of Northern part of Devana Chasma are simultaneous formed.The younger material Unit of South highland of Northern part of Devana Chasma is because of the volcanic eruption of Theia Mons. Conclusion:The physical modeling validates the model of the double plume upwelling is a possible explanation. Acknowledgements:This research was supported by the National Teaching Bases For Geology(CUG)foundation funded. References:[1]I.López,Icarus2008[2]A.T.Basilevsky,Icarus2007[3]J.C.Aubele,2009,LPSC[4]A.V.Vezolainen,2003,Journalofgeophysicalres5earch[5]http://planetarynames.wr.usgs.gov/images/v17_comp&v29_comp.pdf Fig.1 Fig.2 Fig.3a,3b

Ding, N.

2009-12-01

166

[Beta]-Adrenergic Receptors in the Insular Cortex are Differentially Involved in Aversive vs. Incidental Context Memory Formation  

ERIC Educational Resources Information Center

The goal of this research was to determine the effects of [beta]-adrenergic antagonism in the IC before or after inhibitory avoidance (IA) training or context pre-exposure in a latent inhibition protocol. Pretraining intra-IC infusion of the [beta]-adrenergic antagonist propranolol disrupted subsequent IA retention and impaired latent inhibition…

Miranda, Maria Isabel; Sabath, Elizabeth; Nunez-Jaramillo, Luis; Puron-Sierra, Liliana

2011-01-01

167

Cloning, baculovirus expression, and characterization of a second mouse prolyl 4-hydroxylase alpha-subunit isoform: formation of an alpha 2 beta 2 tetramer with the protein disulfide-isomerase/beta subunit.  

PubMed Central

Prolyl 4-hydroxylase (EC 1.14.11.2) catalyzes the posttranslational formation of 4-hydroxyproline in collagens. The vertebrate enzyme is an alpha 2 beta 2 tetramer, the beta subunit of which is a highly unusual multifunctional polypeptide, being identical to protein disulfide-isomerase (EC 5.3.4.1). We report here the cloning of a second mouse alpha subunit isoform, termed the alpha (II) subunit. This polypeptide consists of 518 aa and a signal peptide of 19 aa. The processed polypeptide is one residue longer than the mouse alpha (I) subunit (the previously known type), the cloning of which is also reported here. The overall amino acid sequence identity between the mouse alpha (II) and alpha (I) subunits is 63%. The mRNA for the alpha (II) subunit was found to be expressed in a variety of mouse tissues. When the alpha (II) subunit was expressed together with the human protein disulfide-isomerase/beta subunit in insect cells by baculovirus vectors, an active prolyl 4-hydroxylase was formed, and this protein appeared to be an alpha (II) 2 beta 2 tetramer. The activity of this enzyme was very similar to that of the human alpha (I) 2 beta 2 tetramer, and most of its catalytic properties were also highly similar, but it differed distinctly from the latter in that it was inhibited by poly(L-proline) only at very high concentrations. This property may explain why the type II enzyme was not recognized earlier, as an early step in the standard purification procedure for prolyl 4-hydroxylase is affinity chromatography on a poly(L-proline) column. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:7753822

Helaakoski, T; Annunen, P; Vuori, K; MacNeil, I A; Pihlajaniemi, T; Kivirikko, K I

1995-01-01

168

Wetlands Fact Sheets  

NSDL National Science Digital Library

The U.S. Environmental Protection Agency has provided an extensive list of over 40 fact sheets relating to various aspects of wetlands. Most are provided in a low resoluion format for viewing or a high resolution format for printing. A great deal of basic information regarding the definition, values, and functions of wetlands is provided.

2007-01-07

169

Efficient triple helix formation by oligodeoxyribonucleotides containing alpha- or beta-2-amino-5-(2-deoxy-D-ribofuranosyl) pyridine residues.  

PubMed Central

Triple helices containing C+xGxC triplets are destabilised at physiological pH due to the requirement for base protonation of 2'-deoxycytidine (dC), which has a pKa of 4.3. The C nucleoside 2-amino-5-(2'-deoxy-beta-D-ribofuranosyl)pyridine (beta-AP) is structurally analogous to dC but is considerably more basic, with a pKa of 5.93. We have synthesised 5'-psoralen linked oligodeoxyribonucleotides (ODNs) containing thymidine (dT) and either beta-AP or its alpha-anomer (alpha-AP) and have assessed their ability to form triplexes with a double-stranded target derived from standard deoxynucleotides (i.e. beta-anomers). Third strand ODNs derived from dT and beta-AP were found to have considerably higher binding affinities for the target than the corresponding ODNs derived from dT and either dC or 5-methyl-2'-deoxycytidine (5-Me-dC). ODNs containing dT and alpha-AP also showed enhanced triplex formation with the duplex target and, in addition are more stable in serum-containing medium than standard oligopyrimidine-derived ODNs or ODNs derived from dT and beta-AP. Molecular modelling studies showed that an alpha-anomeric AP nucleotide can be accommodated within an otherwise beta-anomeric triplex with only minor perturbation of the triplex structure. Molecular dynamics (MD) simulations on triplexes containing either the alpha- or beta-anomer of (N1-protonated) AP showed that in both cases the base retained two standard hydrogen bonds to its associated guanine when the 'A-type' model of the triplex was used as the start-point for the simulation, but that bifurcated hydrogen bonds resulted when the alternative 'B-type' triplex model was used. The lack of a differential stability between alpha-AP- and beta-AP-containing triplexes at pH >7, predicted from the behaviour of the B-type models, suggests that the A-type models are more appropriate. PMID:8932369

Bates, P J; Laughton, C A; Jenkins, T C; Capaldi, D C; Roselt, P D; Reese, C B; Neidle, S

1996-01-01

170

Role of Glycogen Synthase Kinase 3beta as a Negative Regulator of Dorsoventral Axis Formation in Xenopus Embryos  

Microsoft Academic Search

The dorsoventral axis is established early in Xenopus development and may involve signaling by Wnts, a family of Wnt1-protooncogene-related proteins. The protein kinase shaggy functions in the wingless\\/Wnt signaling pathway, which operates during Drosophila development. To assess the role of a closely related kinase, glycogen synthase kinase 3beta (GSK-3beta), in vertebrate embryogenesis, we cloned a cDNA encoding a Xenopus homolog

Isabel Dominguez; Keiji Itoh; Sergei Y. Sokol

1995-01-01

171

Fibril stability in solutions of twisted Format="TEX"/>-sheet peptides: a new kind of micellization in chiral systems  

NASA Astrophysics Data System (ADS)

The problem of fibril (fibre) formation in chiral systems is explored theoretically being supported by experiments on synthetic de novo 11-mer peptide forming self-assembled -sheet tapes. Experimental data unambiguously indicate that the tapes form fibrils of nearly monodisperse thickness ca. 8-10 nm. Fibril formation and stabilisation are attributed to inter-tape face-to-face attraction and their intrinsic twist, correspondingly. The proposed theory is capable of predicting the fibril aggregation number and its equilibrium twist in terms of molecular parameters of the primary tapes. The suggested novel mechanism of twist stabilisation of finite aggregates (fibrils) is different to the well-known stabilisation of micelles in amphiphilic systems, and it is likely to explain the formation and stability of fibrils in a wide variety of systems including proteinaceous amyloid fibres, sickle-cell hemoglobin fibres responsible for HbS anemia, corkscrew threads found in chromonics in the presence of chiral additives and native cellulose microfibrillar crystallites. The theory also makes it possible to extract the basic molecular parameters of primary tapes (inter-tape attraction energy, helical twist step, elastic moduli) from the experimental data.

Nyrkova, I. A.; Semenov, A. N.; Aggeli, A.; Boden, N.

2000-10-01

172

Synthesis, folding, and structure of the beta-turn mimic modified B1 domain of streptococcal protein G.  

PubMed Central

The mechanism of beta-sheet formation remains a fundamental issue in our understanding of the protein folding process, but is hampered by the often encountered kinetic competition between folding and aggregation. The role of local versus nonlocal interactions has been probed traditionally by mutagenesis of both turn and strand residues. Recently, rigid organic molecules that impose a correct chain reversal have been introduced in several small peptides to isolate the importance of the long-range interactions. Here, we present the incorporation of a well-studied beta-turn mimic, designated as the dibenzofuran-based (DBF) amino acid, in the B1 domain of streptococcal protein G (B1G), and compare our results with those obtained upon insertion of the same mimic into the N-terminal beta-hairpin of B1G (O Melnyk et al., 1998, Lett Pept Sci 5:147-150). The DBF-B1G domain conserves the structure and the functional and thermodynamical properties of the native protein, whereas the modified peptide does not adopt a native-like conformation. The nature of the DBF flanking residues in the modified B1G domain prevents the beta-turn mimic from acting as a strong beta-sheet nucleator, which reinforces the idea that the native beta-hairpin formation is not driven by the beta-turn formation, but by tertiary interactions. PMID:10631995

Odaert, B.; Jean, F.; Boutillon, C.; Buisine, E.; Melnyk, O.; Tartar, A.; Lippens, G.

1999-01-01

173

Formation of bcc non-equilibrium La, Gd and Dy alloys and the magnetic structure of Mg-stabilized. beta. Gd and. beta. Dy  

SciTech Connect

The high temperature bcc allotrope of a rare earth metal has the potential for substantially different magnetic properties than the room temperature hexagonal (hcp or dhcp) counterpart because of its more symmetrical crystal field. The stabilization by alloying and quenching of this bcc phase was studied for La-M alloys where M is an non-rare earth metal from Group II or III. The factors influencing the stabilization, such as size of M and quench rate, are discussed. ..gamma..La (bcc) could be retained over a composition range around the eutectoid composition by Mg or Cd alloying. A comparison of T/sub o/ curves of the various alloy systems suggest that the eutectoid temperature of the La-M system must be approximately equal to or less than a critical T/sub o/ temperature of 515/degree/C if the bcc phase is to be retained by quenching. The thermal stability of ..beta..Gd (bcc) was investigated by DTA and isothermal annealing. It was found to transform to an intermediate phase before reverting to the equilibrium phases in contrast to ..gamma..La alloys which decompose directly on heating to the equilibrium phases. 71 refs., 52 figs., 7 tabs.

Herchenroeder, J.W.

1989-02-01

174

Non-Equilibrium and Current Sheet Formation in Line-Tied Magneti... http://www.aps.org/meet/DPP02/baps/abs/S670004.html 1 of 1 3/10/05 10:26 AM  

E-print Network

, for a system periodic in the transverse directions. It follows that if such a static equilibrium is drivenNon-Equilibrium and Current Sheet Formation in Line-Tied Magneti... http://www.aps.org/meet/DPP02 and Dynamics III. ORAL session, Tuesday morning, November 12 Salon 5-6, Rosen Centre Hotel [FM1.004] Non-Equilibrium

Ng, Chung-Sang

175

?-Sheet Pore-Forming Peptides Selected from a Rational Combinatorial Library: Mechanism of Pore Formation in Lipid Vesicles and Activity in Biological Membranes†  

PubMed Central

In a previous report we described the selection of potent, ?-sheet pore-forming peptides from a combinatorial library designed to mimic membrane-spanning ?-hairpins (Rausch JM, Marks JR and Wimley WC, (2005) PNAS, 102:10511-5). Here, we characterize their mechanism of action and compare the structure-function relationships in lipid vesicles to their activity in biological membranes. The pore-forming peptides bind to membrane interfaces and self-assemble into ?-sheets that cause a transient burst of graded leakage across the bilayers. Despite the continued presence of the structured peptides in the bilayer, at most peptide concentrations leakage is incomplete and ceases quickly after peptide addition with a deactivation half-time of several minutes. Molecules up to 3,000 Da escape from the transient pores, but much larger molecules do not. Fluorescence spectroscopy and quenching showed that the peptides reside mainly on the bilayer surface and are partially exposed to water, rather than in a membrane-spanning state. The “carpet” or “sinking raft” model of peptide pore formation offers a viable explanation for our observations and suggests that the selected pore formers function with a mechanism that is similar to the natural pore-forming antimicrobial peptides. We therefore also characterized the antimicrobial and cytotoxic activity of these peptides. All peptides studied, including non pore-formers, had sterilizing antimicrobial activity against at least some microbes, and most have low activity against mammalian cell membranes. Thus, the structure-function relationships that were apparent in the vesicle systems are similar to, but do not correlate completely with the activity of the same peptides in biological membranes. However, of the peptides tested, only the pore-formers selected in the high throughput screen have potent, broad-spectrum sterilizing activity against Gram-positive and Gram-negative bacteria as well as against fungi, while having only small lytic effects on human cells. PMID:17918962

Rausch, Joshua M.; Marks, Jessica R.; Rathinakumar, Ramesh; Wimley, William C.

2008-01-01

176

Disintegration of liquid sheets  

NASA Technical Reports Server (NTRS)

The development, stability, and disintegration of liquid sheets issuing from a two-dimensional air-assisted nozzle is studied. Detailed measurements of mean drop size and velocity are made using a phase Doppler particle analyzer. Without air flow the liquid sheet converges toward the axis as a result of surface tension forces. With airflow a quasi-two-dimensional expanding spray is formed. The air flow causes small variations in sheet thickness to develop into major disturbances with the result that disruption starts before the formation of the main break-up region. In the two-dimensional variable geometry air-blast atomizer, it is shown that the air flow is responsible for the formation of large, ordered, and small chaotic 'cell' structures.

Mansour, Adel; Chigier, Norman

1990-01-01

177

Hydrogen- Facts Sheet  

NSDL National Science Digital Library

This fact sheet provides some basic information about hydrogen. Hydrogen's history, physical and chemical properties, the production of hydrogen, details on how it is stored, safety tips for working with hydrogen and reasons for using hydrogen are outlined. This document may be downloaded in PDF file format.

2011-12-26

178

Determination of isoprene and alpha-/beta-pinene oxidation products in boreal forest aerosols from Hyytiälä, Finland: diel variations and possible link with particle formation events.  

PubMed

Biogenic volatile organic compounds (VOCs), such as isoprene and alpha-/beta-pinene, are photo-oxidized in the atmosphere to non-volatile species resulting in secondary organic aerosol (SOA). The goal of this study was to examine time trends and diel variations of oxidation products of isoprene and alpha-/beta-pinene in order to investigate whether they are linked with meteorological parameters or trace gases. Separate day-night aerosol samples (PM(1)) were collected in a Scots pine dominated forest in southern Finland during 28 July-11 August 2005 and analyzed with gas chromatography/mass spectrometry (GC/MS). In addition, inorganic trace gases (SO(2), CO, NO(x), and O(3)), meteorological parameters, and the particle number concentration were monitored. The median total concentration of terpenoic acids (i.e., pinic acid, norpinic acid, and two novel compounds, 3-hydroxyglutaric acid and 2-hydroxy-4-isopropyladipic acid) was 65 ng m(-3), while that of isoprene oxidation products (i.e., 2-methyltetrols and C(5) alkene triols) was 17.2 ng m(-3). The 2-methyltetrols exhibited day/night variations with maxima during day-time, while alpha-/beta-pinene oxidation products did not show any diel variation. The sampling period was marked by a relatively high condensation sink, caused by pre-existing aerosol particles, and no nucleation events. In general, the concentration trends of the SOA compounds reflected those of the inorganic trace gases, meteorological parameters, and condensation sink. Both the isoprene and alpha-/beta-pinene SOA products were strongly influenced by SO(2), which is consistent with earlier reports that acidity plays a role in SOA formation. The results support previous proposals that oxygenated VOCs contribute to particle growth processes above boreal forest. PMID:18211553

Kourtchev, I; Ruuskanen, T M; Keronen, P; Sogacheva, L; Dal Maso, M; Reissell, A; Chi, X; Vermeylen, R; Kulmala, M; Maenhaut, W; Claeys, M

2008-01-01

179

Overexpression of granulocyte-macrophage colony-stimulating factor induces pulmonary granulation tissue formation and fibrosis by induction of transforming growth factor-beta 1 and myofibroblast accumulation.  

PubMed Central

We have previously reported that transfer to rat lung of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene leads to high expression of GM-CSF between days 1 and 4 and granulation tissue formation followed by an irreversible fibrotic response starting from day 12 onward. In the current study, we investigated the underlying mechanisms. We found that GM-CSF overexpression did not enhance production of tumor necrosis factor-alpha in a significant manner at any time after GM-CSF gene transfer. However, the content of transforming growth factor-beta 1 in bronchoalveolar lavage fluid was markedly induced at day 4 and appeared to be maximal around day 7 and remained high at day 12. Macrophages purified from bronchoalveolar lavage fluid 7 days after GM-CSF gene transfer spontaneously released significant quantities of transforming growth factor-beta 1 protein in vitro. After peak transforming growth factor-beta 1 production was the emergence of alpha-smooth muscle actin-rich myofibroblasts. Accumulation of these cells was most prominent at day 12 within the granulation tissues and they were still present in fibrotic areas between days 12 and 24 and diminished markedly afterward. Thus, we provide the first in vivo evidence that tumor necrosis factor-alpha may be dissociated from participation in a fibrotic process in the lung and GM-CSF may play a more direct role in pulmonary fibrogenesis at least in part through its capability to induce transforming growth factor-beta 1 in macrophages and the subsequent emergence of myofibroblast phenotypes. This GM-CSF transgene lung model is useful for a stepwise dissection of both cellular and molecular events involved in pulmonary fibrosis. Images Figure 2 Figure 5 Figure 6 PMID:9006322

Xing, Z.; Tremblay, G. M.; Sime, P. J.; Gauldie, J.

1997-01-01

180

Estrogen treatment improves spatial learning in APP + PS1 mice but does not affect beta amyloid accumulation and plaque formation  

Microsoft Academic Search

We investigated the effects of ovariectomy (OVX) and 17?-estradiol (0.18 mg per pellet) treatment on spatial learning and memory, hippocampal beta amyloid (A?) levels, and amyloid plaque counts in double transgenic mice (A\\/P) carrying mutated amyloid precursor protein (APPswe) and presenilin-1 (PS1-A246E). After OVX at 3 months of age, the mice received estrogen treatment for the last 3 months of

T. Heikkinen; G. Kalesnykas; A. Rissanen; T. Tapiola; S. Iivonen; J. Wang; J. Chaudhuri; H. Tanila; R. Miettinen; J. Puoliväli

2004-01-01

181

A calorimetric determination of the enthalpy of formation and a description of the defect structure of the ordered beta-phase /Ni, Cu/ /1-x/ Al/x/  

NASA Technical Reports Server (NTRS)

In order to describe thermodynamically the defect structure of an ordered B-Hume-Rothery phase, the heat of formation of (Ni,Cu)(1-x)Al(x) was measured at 1100 K as a function of concentration in the range x (sub Al) = 0.4 and 0.55 for three substitution rations x (sub Ni)/x (sub Cu) = infinity; 11; 5. The heat of formation of the NiAl beta-phase is strongly negative. For the stoichiometric composition it is -72.2 kJ/g-atom. On both the nickel-rich side and the aluminum-rich side the magnitude of the enthalpy of formation decreases linearly with concentration. Substitution of nickel for copper decreases the magnitude of the enthalpy of formation over the entire homogeneity range for the phase (Ni,Cu)(1-x)Al(x). The curve for the enthalpy of formation as well as the literature values for the chemical potential of aluminum are described with great accuracy by the disorder model of Wagner-Schottky.

Henig, E. T.; Lukas, H. L.

1988-01-01

182

Evidence of formation of site-selective inclusion complexation between beta-cyclodextrin and poly(ethylene oxide)-block-poly(propylene oxide)- block-poly(ethylene oxide) copolymers.  

PubMed

A series of inclusion complexes of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b-PPO-b-PEO) with beta-cyclodextrin (beta-CD) was prepared. Their formation, structure, and dynamics were investigated by solution two-dimensional rotating-frame Overhauser effect spectroscopy (2D ROESY) and one-dimensional (1D) and 2D solid-state (13)C NMR. The inclusion complexes between the PEO-b-PPO-b-PEO copolymers and the beta-CDs were formed in aqueous solution and detected by 2D ROESY. The high efficiency of cross polarization and spin diffusion experiments in (13)C solid-state NMR showed that the mobility of the PPO blocks dramatically decreases after beta-CD complexation, indicating that they are selectively incorporated onto the PPO blocks. The hydrophobic cavities of beta-CD restrict the PPO block mobility, which is evidence of the formation of inclusion complexes in the solid state. The 2D wide-line separation NMR experiments suggested that beta-CDs only thread onto the PPO blocks while forming the inclusion complexes. The stoichiometry of inclusion complexes was studied using (1)H NMR, and a 3:1 (PO unit to beta-CD) was found for all inclusion complexes, which indicated that the number of threaded beta-CDs was only dependent on the molecular weight of the PPO blocks. 1D wide angle x-ray diffraction studies demonstrated that the beta-CD in the inclusion complex formed a channel-like structure that is different from the pure beta-CD crystal structure. PMID:20515110

Tsai, Chi-Chun; Zhang, Wen-Bin; Wang, Chien-Lung; Van Horn, Ryan M; Graham, Matthew J; Huang, Jing; Chen, Yongming; Guo, Mingming; Cheng, Stephen Z D

2010-05-28

183

-Sheet Pore-Forming Peptides Selected from a Rational Combinatorial Library: Mechanism of Pore Formation in Lipid Vesicles and Activity in Biological  

E-print Network

-Sheet Pore-Forming Peptides Selected from a Rational Combinatorial Library: Mechanism of Pore the selection of potent, -sheet pore-forming peptides from a combinatorial library designed to mimic membrane in lipid vesicles to their activity in biological membranes. The pore-forming peptides bind to membrane

Wimley, William C.

184

Fibers of tau fragments, but not full length tau, exhibit a cross beta-structure: implications for the formation of paired helical filaments.  

PubMed Central

We have used X-ray fiber diffraction to probe the structure of fibers of tau and tau fragments. Fibers of fragments from the microtubule binding domain had a cross beta-structure that closely resembles that reported both for neurofibrillary tangles found in Alzheimer's disease brain and for fibrous lesions from other protein folding diseases. In contrast, fibers of full-length tau had a different, more complex structure. Despite major differences at the molecular level, all fiber types exhibited very similar morphology by electron microscopy. These results have a number of implications for understanding the etiology of Alzheimer's and other tauopathic diseases. The morphology of the peptide fibers suggests that the region in tau corresponding to the peptides plays a critical role in the nucleation of fiber assembly. The dramatically different structure of the full length tau fibers suggests that some region in tau has enough inherent structure to interfere with the formation of cross beta-fibers. Additionally, the similar appearance by electron microscopy of fibrils with varying molecular structure suggests that different molecular arrangements may exist in other samples of fibers formed from tau. PMID:11206064

Giannetti, A. M.; Lindwall, G.; Chau, M. F.; Radeke, M. J.; Feinstein, S. C.; Kohlstaedt, L. A.

2000-01-01

185

Study on the Formation and Characterization of the Intermetallics in Friction Stir Welding of Aluminum Alloy to Coated Steel Sheet Lap Joint  

NASA Astrophysics Data System (ADS)

Multimaterial fabrication such as joining of steel and aluminum is currently prominent in a variety of industries. Friction stir welding is a novel solid-state welding process that causes good joint strength between steel and aluminum. However, the phenomenon contributing significant strength at the interface is not yet clear. In the present study, the interface of the friction stir lap-welded aluminum and coated steel sheet having joint strength maximum (71.4 pct of steel base metal) and minimum, respectively, under two parameter combinations, i.e., 1000 rpm 50 mm min-1 and 500 rpm 100 mm min-1, was exclusively characterized by X-ray diffraction, transmission electron microscopy (TEM), concentration profile, and elemental mapping by electron-probe microanalysis. A TEM-assisted EDS study identifies the morphologies of large size Al13Fe4 and small size Fe3Al-type intermetallic compounds at the interface. The diffusion-induced intermetallic growth (thickness) measured from a backscattered image and concentration profile agreed well with the numerically calculated one. The growth of these two phases at 1000 rpm 50 mm min-1 is attributed to the slower cooling rate (~3.5 K/s) with higher diffusion time (44 seconds) along the interface in comparison to the same for 500 rpm 100 mm min-1 with faster cooling rate (~10 K/s) and less diffusion time (13.6 seconds). The formation of thermodynamically stable and hard intermetallic phase Al13Fe4 at 1000 rpm and travel speed 50 mm min-1 in amounts higher than 500 rpm and a travel speed of 100 mm min-1 results in better joint strength, i.e., 71.4 pct, of the steel base metal.

Das, H.; Ghosh, R. N.; Pal, T. K.

2014-10-01

186

Overexpression of protein kinase C. beta. 1 enhances phospholipase D activity and diacylglycerol formation in phorbol ester-stimulated rat fibroblasts  

SciTech Connect

The authors are using a Rat-6 fibroblast cell line that stably overexpresses the {beta}1 isozyme of protein kinase C (PKC) to study regulation of phospholipid hydrolysis by PKC. Stimulation of control (R6-C1) or overexpressing (R6-PKC3) cells with phorbol ester results in an increase in diacylglycerol (DAG) mass with no increase in inositol phosphates, indicating that DAG is not formed by inositol phospholipid breakdown. A more dramatic DAG increase occurs in R6-PKC3 cells compared to R6-C1 cells. To further define the source of DAG, phosphatidylcholine (PC) pools were labeled with ({sup 3}H)myristic acid or with ({sup 3}H)- or ({sup 32}P)alkyllyso-PC and formation of labeled phosphatidylethanol, an unambiguous marker of phospholipase D activation, was monitored. Phorbol ester-stimulated phosphatidylethanel formation is 5-fold greater in the R6-PKC3 cell line. Formation of radiolabeled phosphatidic acid (PA) is also enhanced by PKC overepression. In cells double-labeled with ({sup 3}H)- and ({sup 32}P)-alkyl-lysoPC, the {sup 3}H/{sup 32}P ratio of PA and PC are identical 15 min after stimulation, suggesting that a phospholipase D mechanism predominates. These results indicate that phospholipase D is regulated by the action of PKC. Enhanced phospholipase D activity may contribute to the growth abnormalities seen in PKC-overexpressing cells.

Pai, Jinkeon; Pachter, J.A.; Bishop, W.R. (Schering-Plough Research, Bloomfield, NJ (United States)); Weinstein, I.B. (Columbia Univ., New York, NY (United States))

1991-01-15

187

Ensemble modeling of [beta]-sheet proteins  

E-print Network

Our ability to characterize protein structure and dynamics is vastly outpaced by the speed of modern genetic sequencing, creating a growing divide between our knowledge of biological sequence and structure. Structural ...

O'Donnell, Charles William

2011-01-01

188

Reelin delays amyloid-beta fibril formation and rescues cognitive deficits in a model of Alzheimer's disease.  

PubMed

Reelin is an extracellular matrix protein that is crucial for neural development and adult brain plasticity. While the Reelin signalling cascade has been reported to be associated with Alzheimer's disease (AD), the role of Reelin in this pathology is not understood. Here we use an in vitro approach to show that Reelin interacts with amyloid-? (A?42) soluble species, delays A?42 fibril formation and is recruited into amyloid fibrils. Furthermore, Reelin protects against both the neuronal death and dendritic spine loss induced by A?42 oligomers. In mice carrying the APP(Swe/Ind) mutation (J20 mice), Reelin overexpression delays amyloid plaque formation and rescues the recognition memory deficits. Our results indicate that by interacting with A?42 soluble species, delaying A? plaque formation, protecting against neuronal death and dendritic spine loss and preventing AD cognitive deficits, the Reelin pathway deserves consideration as a therapeutic target for the treatment of AD pathogenesis. PMID:24599114

Pujadas, Lluís; Rossi, Daniela; Andrés, Rosa; Teixeira, Cátia M; Serra-Vidal, Bernat; Parcerisas, Antoni; Maldonado, Rafael; Giralt, Ernest; Carulla, Natàlia; Soriano, Eduardo

2014-01-01

189

Beta amyloid and hyperphosphorylated tau deposits in the pancreas in type 2 diabetes  

SciTech Connect

Strong epidemiologic evidence suggests an association between Alzheimer disease (AD) and type 2 diabetes. To determine if amyloid beta (A{beta}) and hyperphosphorylated tau occurs in type 2 diabetes, pancreas tissues from 21 autopsy cases (10 type 2 diabetes and 11 controls) were analyzed. APP and tau mRNAs were identified in human pancreas and in cultured insulinoma beta cells (INS-1) by RT-PCR. Prominent APP and tau bands were detected by Western blotting in pancreatic extracts. Aggregated A{beta}, hyperphosphorylated tau, ubiquitin, apolipoprotein E, apolipoprotein(a), IB1/JIP-1 and JNK1 were detected in Langerhans islets in type 2 diabetic patients. A{beta} was co-localized with amylin in islet amyloid deposits. In situ beta sheet formation of islet amyloid deposits was shown by infrared microspectroscopy (SIRMS). LPS increased APP in non-neuronal cells as well. We conclude that A{beta} deposits and hyperphosphorylated tau are also associated with type 2 diabetes, highlighting common pathogenetic features in neurodegenerative disorders, including AD and type 2 diabetes and suggesting that A{beta} deposits and hyperphosphorylated tau may also occur in other organs than the brain.

Miklossy, J.; Miller, L.; Qing, H.; Radenovic, A.; Kis, A.; Vileno, B.; Laszlo, F.; Martins, R.N.; Waeber, G.; Mooser, V.; Bosman, F.; Khalili, K.; Darbinian, N.; McGeer, P.L.

2008-08-25

190

Association for Women in Beta Beta Beta  

E-print Network

(Honor Society) MusicSymphonic BandUniversity SymphonyOrchestraWomen's ChorusMen's ChorusConcert ChoraleBiology Association for Women in Science (A.W.I.S.) Beta Beta Beta (National Honor Society) Sigma(Conversation Table)Sigma Delta Pi(National Honor Society) Theatre and FilmUT Film and VideoSocietyAlpha Psi Omega

Viola, Ronald

191

Hydroxylated metabolites of beta- and delta-hexachlorocyclohexane: bacterial formation, stereochemical configuration, and occurrence in groundwater at a former production site.  

PubMed

Although the use of hexachlorocyclohexane (HCH), one of the most popular insecticides after the Second World War, has been discontinued in many countries, problems remain from former production and waste sites. Despite the widespread occurrence of HCHs, the environmental fate of these compounds is not fully understood. In particular, environmental metabolites of the more persistent beta-HCH and delta-HCH have not been fully identified. Such knowledge, however, is important to follow degradation and environmental fate of the HCHs. In the present study, several hydroxy metabolites that formed during incubation of beta- and delta-HCH with the common soil microorganism Sphingobium indicum B90A were isolated, characterized, and stereochemically identified by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). The metabolites were identified as isomeric pentachlorocyclohexanols (B1, D1) and tetrachlorocyclohexane-1,4-diols (B2, D2); delta-HCH additionally formed a tetrachloro-2-cyclohexen-1-ol (D3) and a trichloro-2-cyclohexene-1,4-diol (D4), most likely by hydroxylation of delta-pentachlorocyclohexene (delta-PCCH), initially formed by dehydrochlorination. The dehydrochlorinase LinA was responsible for conversion of delta-HCH into delta-PCCH, and the haloalkane dehalogenase LinB was responsible for the transformation of beta-HCH and delta-HCH into B1 and D1, respectively, and subsequently into B2 and D2, respectively. LinB was also responsible for transforming delta-PCCH into D3 and subsequently into D4. These hydroxylations proceeded in accordance with SN2 type reactions with initial substitution of equatorial Cls and formation of axially hydroxylated stereoisomers. The apparently high reactivity of equatorial Cls in beta- and delta-HCH toward initial hydroxylation by LinB of Sphingobium indicum B90A is remarkable when considering the otherwise usually higher reactivity of axial Cls. Several of these metabolites were detected in groundwater from a former HCH production site in Switzerland. Their presence indicates that these reactions proceed under natural environmental conditions and that the metabolites are of environmental relevance. PMID:17626427

Raina, Vishakha; Hauser, Andrea; Buser, Hans Rudolf; Rentsch, Daniel; Sharma, Poonam; Lal, Rup; Holliger, Christof; Poiger, J Thomas; Müller, Markus D; Kohler, Hans-Peter E

2007-06-15

192

Ablation of MMP9 gene ameliorates paracellular permeability and fibrinogen-amyloid beta complex formation during hyperhomocysteinemia.  

PubMed

Increased blood level of homocysteine (Hcy), called hyperhomocysteinemia (HHcy) accompanies many cognitive disorders including Alzheimer's disease. We hypothesized that HHcy-enhanced cerebrovascular permeability occurs via activation of matrix metalloproteinase-9 (MMP9) and leads to an increased formation of fibrinogen-?-amyloid (Fg-A?) complex. Cerebrovascular permeability changes were assessed in C57BL/6J (wild type, WT), cystathionine-?-synthase heterozygote (Cbs+/-, a genetic model of HHcy), MMP9 gene knockout (Mmp9-/-), and Cbs and Mmp9 double knockout (Cbs+/-/Mmp9-/-) mice using a dual-tracer probing method. Expression of vascular endothelial cadherin (VE-cadherin) and Fg-A? complex formation was assessed in mouse brain cryosections by immunohistochemistry. Short-term memory of mice was assessed with a novel object recognition test. The cerebrovascular permeability in Cbs+/- mice was increased via mainly the paracellular transport pathway. VE-cadherin expression was the lowest and Fg-A? complex formation was the highest along with the diminished short-term memory in Cbs+/- mice. These effects of HHcy were ameliorated in Cbs+/-/Mmp9-/- mice. Thus, HHcy causes activation of MMP9 increasing cerebrovascular permeability by downregulation of VE-cadherin resulting in an enhanced formation of Fg-A? complex that can be associated with loss of memory. These data may lead to the identification of new targets for therapeutic intervention that can modulate HHcy-induced cerebrovascular permeability and resultant pathologies. PMID:24865997

Muradashvili, Nino; Tyagi, Reeta; Metreveli, Naira; Tyagi, Suresh C; Lominadze, David

2014-09-01

193

A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field  

NASA Astrophysics Data System (ADS)

Orbital limited motion theory has been applied to two biased probes in a low beta Polywell. The cases studied include electron injection, magnetic field scaling, Polywell bias scaling, and radial position profiles. Langmuir's original orbital limited motion results for a monoenergetic electron beam are shown to be in excellent agreement for electron injection into the Polywell. A distribution function is proposed for the electron plasma characteristics in the centre of the magnetic null and confirmed with experimental results. A translational stage was used to measure the radial plasma potential profile. In other experiments, two probes were used to simultaneously measure the profiles in both the null and a position halfway along a corner cusp. The results confirm a radial potential well created by electron trapping in the device. In addition, we present preliminary results of the potential well scaling with the magnetic field, Polywell bias voltage, and the injected beam current. The electron population was found to maintain non-equilibrium in all cases studied.

Carr, Matthew; Khachan, Joe

2013-05-01

194

A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field  

SciTech Connect

Orbital limited motion theory has been applied to two biased probes in a low beta Polywell. The cases studied include electron injection, magnetic field scaling, Polywell bias scaling, and radial position profiles. Langmuir's original orbital limited motion results for a monoenergetic electron beam are shown to be in excellent agreement for electron injection into the Polywell. A distribution function is proposed for the electron plasma characteristics in the centre of the magnetic null and confirmed with experimental results. A translational stage was used to measure the radial plasma potential profile. In other experiments, two probes were used to simultaneously measure the profiles in both the null and a position halfway along a corner cusp. The results confirm a radial potential well created by electron trapping in the device. In addition, we present preliminary results of the potential well scaling with the magnetic field, Polywell bias voltage, and the injected beam current. The electron population was found to maintain non-equilibrium in all cases studied.

Carr, Matthew; Khachan, Joe [Department of Plasma Physics, School of Physics A28, University of Sydney NSW 2006 (Australia)] [Department of Plasma Physics, School of Physics A28, University of Sydney NSW 2006 (Australia)

2013-05-15

195

Enhanceosome Formation over the Beta Interferon Promoter Underlies a Remote-Control Mechanism Mediated by YY1 and YY2  

PubMed Central

The expression of beta interferon genes from humans and mice is under the immediate control of a virus-responsive element (VRE) that terminates 110 bp upstream from the transcriptional start site. Whereas a wealth of information is available for the enhanceosome that is formed on the VRE upon the signals generated by viral infection, early observations indicating the existence of other far-upstream control elements have so far remained without a molecular fundament. Guided by a computational analysis of DNA structures, we could locate three as-yet-unknown transcription factor-binding regions at ?0.5, ?2, and ?3 kb. Our present study delineates the interplay of factors YY1 and YY2 as it occurs at the sites at ?3 kb and ?2 kb (otherwise called HS1 and HS2), consistent with the idea that the novel factor YY2 antagonizes the negative actions exerted by YY1. Differences between the human and murine control regions will be described. PMID:16260628

Klar, Martin; Bode, Juergen

2005-01-01

196

The motion of thrust sheets  

Microsoft Academic Search

The regional average basal shear stress tau of a thrust sheet of thickness H is equal to the down-surface slope stress pgHalpha. Thrusts always move in the direction of surface slope alpha, even if they are moving up the dip beta of the base. The sole thrust beneath the Canadian Rockies had tau of the order of 5×106 Pa (50

David Elliott

1976-01-01

197

Interaction of the Molecular Chaperone DNAJB6 with Growing Amyloid-beta 42 (A?42) Aggregates Leads to Sub-stoichiometric Inhibition of Amyloid Formation.  

PubMed

The human molecular chaperone protein DNAJB6 was recently found to inhibit the formation of amyloid fibrils from polyglutamine peptides associated with neurodegenerative disorders such as Huntington disease. We show in the present study that DNAJB6 also inhibits amyloid formation by an even more aggregation-prone peptide (the amyloid-beta peptide, A?42, implicated in Alzheimer disease) in a highly efficient manner. By monitoring fibril formation using Thioflavin T fluorescence and far-UV CD spectroscopy, we have found that the aggregation of A?42 is retarded by DNAJB6 in a concentration-dependent manner, extending to very low sub-stoichiometric molar ratios of chaperone to peptide. Quantitative kinetic analysis and immunochemistry studies suggest that the high inhibitory efficiency is due to the interactions of the chaperone with aggregated forms of A?42 rather than the monomeric form of the peptide. This interaction prevents the growth of such species to longer fibrils and inhibits the formation of new amyloid fibrils through both primary and secondary nucleation. A low dissociation rate of DNAJB6 from A?42 aggregates leads to its incorporation into growing fibrils and hence to its gradual depletion from solution with time. When DNAJB6 is eventually depleted, fibril proliferation takes place, but the inhibitory activity can be prolonged by introducing DNAJB6 at regular intervals during the aggregation reaction. These results reveal the highly efficacious mode of action of this molecular chaperone against protein aggregation, and demonstrate that the role of molecular chaperones can involve interactions with multiple aggregated species leading to the inhibition of both principal nucleation pathways through which aggregates are able to form. PMID:25217638

Månsson, Cecilia; Arosio, Paolo; Hussein, Rasha; Kampinga, Harm H; Hashem, Reem M; Boelens, Wilbert C; Dobson, Christopher M; Knowles, Tuomas P J; Linse, Sara; Emanuelsson, Cecilia

2014-11-01

198

Interaction of the Molecular Chaperone DNAJB6 with Growing Amyloid-beta 42 (A?42) Aggregates Leads to Sub-stoichiometric Inhibition of Amyloid Formation*  

PubMed Central

The human molecular chaperone protein DNAJB6 was recently found to inhibit the formation of amyloid fibrils from polyglutamine peptides associated with neurodegenerative disorders such as Huntington disease. We show in the present study that DNAJB6 also inhibits amyloid formation by an even more aggregation-prone peptide (the amyloid-beta peptide, A?42, implicated in Alzheimer disease) in a highly efficient manner. By monitoring fibril formation using Thioflavin T fluorescence and far-UV CD spectroscopy, we have found that the aggregation of A?42 is retarded by DNAJB6 in a concentration-dependent manner, extending to very low sub-stoichiometric molar ratios of chaperone to peptide. Quantitative kinetic analysis and immunochemistry studies suggest that the high inhibitory efficiency is due to the interactions of the chaperone with aggregated forms of A?42 rather than the monomeric form of the peptide. This interaction prevents the growth of such species to longer fibrils and inhibits the formation of new amyloid fibrils through both primary and secondary nucleation. A low dissociation rate of DNAJB6 from A?42 aggregates leads to its incorporation into growing fibrils and hence to its gradual depletion from solution with time. When DNAJB6 is eventually depleted, fibril proliferation takes place, but the inhibitory activity can be prolonged by introducing DNAJB6 at regular intervals during the aggregation reaction. These results reveal the highly efficacious mode of action of this molecular chaperone against protein aggregation, and demonstrate that the role of molecular chaperones can involve interactions with multiple aggregated species leading to the inhibition of both principal nucleation pathways through which aggregates are able to form. PMID:25217638

Mansson, Cecilia; Arosio, Paolo; Hussein, Rasha; Kampinga, Harm H.; Hashem, Reem M.; Boelens, Wilbert C.; Dobson, Christopher M.; Knowles, Tuomas P. J.; Linse, Sara; Emanuelsson, Cecilia

2014-01-01

199

Generation of an rhBMP-2-loaded beta-tricalcium phosphate/hydrogel composite and evaluation of its efficacy on peri-implant bone formation.  

PubMed

Dental implant insertion on a site with low bone quality or bone defect should be preceded by a bone graft or artificial bone graft insertion to heal the defect. We generated a beta-tricalcium phosphate (?-TCP) and poloxamer 407-based hydrogel composite and penetration of the ?-TCP/hydrogel composite into the peri-implant area of bone was evaluated by porous bone block experiments. The maximum penetration depth for porous bone blocks and dense bone blocks were 524??m and 464??m, respectively. We report the in-vivo performance of a composite of ?-TCP/hydrogel composite as a carrier of recombinant human bone morphogenetic protein (rhBMP-2), implanted into a rabbit tibial defect model. Three holes drilled into each tibia of eight male rabbits were (1) grafted with dental implant fixtures; (2) filled with ?-TCP/hydrogel composite (containing 5??g of rhBMP-2), followed by grafting of the dental implant fixtures. Four weeks later, bone-implant contact ratio and peri-implant bone formation were analyzed by radiography, micro-CT and histology of undecalcified specimens. The micro-CT results showed a significantly higher level of trabecular thickness and new bone and peri-implant new bone formation in the experimental treatment compared to the control treatment. Histomorphometry revealed a significantly higher bone-implant contact ratio and peri-implant bone formation with the experimental treatment. The use of ?-TCP/poloxamer 407 hydrogel composite as a carrier of rhBMP-2 significantly promoted new bone formation around the dental implant fixture and it also improved the quality of the new bone formed in the tibial marrow space. PMID:25135209

Lee, Jae Hyup; Ryu, Mi Young; Baek, Hae-Ri; Seo, Jun-Hyuk; Lee, Kyung-Mee; Lee, Ji-Ho

2014-10-01

200

beta-amyloid deposition and neurofibrillary tangle formation in the olfactory bulb in ageing and Alzheimer's disease.  

PubMed

Impaired olfaction, hyposmia or anosmia are part of the clinical phenotype in neurodegenerative disorders including Alzheimer's disease (AD). It has been proposed that the most severely affected areas are interconnected with the central olfactory system in contrast to the relative sparing of other sensory areas which lack olfactory connections. The pathology of the first synaptic relay in the olfactory pathway, the olfactory bulb (OB), has been studied in AD, but the results have been inconsistent. In order to define more fully the pathology of the OB, we analysed 15 AD and 15 control cases, using amyloid and tau immunohistochemistry on serial sections. This study demonstrates for the first time that all layers of the OB are severely affected in AD and in normal ageing. The principal effector cells of the OB, the mitral cells, developed neurofibrillary tangles (NFTs) both in AD and in controls. All the cases, with the exception of two of the controls, contained NFTs. Amyloid immunoreactivity was detected in diffuse, primitive, classical and compact deposits in AD, while five control cases contained mainly diffuse deposits. We did not find a correlation between amyloid deposition and NFT formation. Among the control cases, two contained neither amyloid nor NFTs, eight had NFTs but no amyloid and only five had both NFTs and amyloid. All the AD cases had NFT and amyloid deposition. Our data suggest that the earlier pathology in the OB is NFT formation and more than ten NFTs/section is compatible with 93.3% diagnostic accuracy for AD. PMID:10632898

Kovács, T; Cairns, N J; Lantos, P L

1999-12-01

201

Oncoprotein E7 from Beta Human Papillomavirus 38 Induces Formation of an Inhibitory Complex for a Subset of p53-Regulated Promoters  

PubMed Central

Our previous studies on cutaneous beta human papillomavirus 38 (HPV38) E6 and E7 oncoproteins highlighted a novel activity of I?B kinase beta (IKK?) in the nucleus of human keratinocytes, where it phosphorylates and stabilizes ?Np73?, an antagonist of p53/p73 functions. Here, we further characterize the role of the IKK? nuclear form. We show that IKK? nuclear translocation and ?Np73? accumulation are mediated mainly by HPV38 E7 oncoprotein. Chromatin immunoprecipitation (ChIP)/Re-ChIP experiments showed that ?Np73? and IKK? are part, together with two epigenetic enzymes DNA methyltransferase 1 (DNMT1) and the enhancer of zeste homolog 2 (EZH2), of a transcriptional regulatory complex that inhibits the expression of some p53-regulated genes, such as PIG3. Recruitment to the PIG3 promoter of EZH2 and DNMT1 resulted in trimethylation of histone 3 on lysine 27 and in DNA methylation, respectively, both events associated with gene expression silencing. Decreases in the intracellular levels of HPV38 E7 or ?Np73? strongly affected the recruitment of the inhibitory transcriptional complex to the PIG3 promoter, with consequent restoration of p53-regulated gene expression. Finally, the ?Np73?/IKK?/DNMT1/EZH2 complex appears to bind a subset of p53-regulated promoters. In fact, the complex is efficiently recruited to several promoters of genes encoding proteins involved in DNA repair and apoptosis, whereas it does not influence the expression of the prosurvival factor Survivin. In summary, our data show that HPV38 via E7 protein promotes the formation of a multiprotein complex that negatively regulates the expression of several p53-regulated genes. PMID:24006445

Saidj, Djamel; Cros, Marie-Pierre; Hernandez-Vargas, Hector; Guarino, Francesca; Sylla, Bakary S.; Tommasino, Massimo

2013-01-01

202

Influence of t-butylhydroquinone and beta-naphthoflavone on formation and transport of 4-methylumbelliferone glucuronide in Caco-2/TC-7 cell monolayers.  

PubMed

Human Caco-2 cells have been established as a model system for intestinal biotransformation and permeability. When grown on Transwell polycarbonate filters they develop morphologic and biochemical characteristics of enterocytes with well separated apical and basolateral surfaces. In addition, Caco-2/TC-7 cells have proven to be useful to study regulation of human UDP-glucuronosyltransferases (UGTs) by Ah receptor agonists and antioxidant-type inducers such as beta-naphthoflavone (BNF) and t-butylhydroquinone (TBHQ). In the present investigation, formation and transport of 4-methylumbelliferone glucuronide was studied in intact Caco-2 cell monolayers. The following results were obtained: when loaded with 50-200 microM MUF either apically or basolaterally, MUF-GA was the major metabolite which was mostly released (80%) at the basolateral surface, probably via the multidrug resistance protein isoform MRP3; MUF sulfate formation was low (5 +/-2%). Pretreatment of cells with 80 microM TBHQ or 50 microM BNF for 72 hr before addition of 100 microM MUF enhanced basolateral secretion of MUF-GA 1.4- and 1.7-fold, respectively. However, at >200 microM MUF, MUF-GA secretion and induction was smaller, probably due to inhibition of intracellular UGT activity. MRP3 protein was localized to the basolateral surface of Caco-2 cells but was not induced by TBHQ or BNF. The results suggest that MUF-GA is mostly secreted basolaterally in Caco-2 cell monolayers. Treatment with TBHQ or BNF significantly enhanced MUF-GA formation in the intact cell. PMID:11841785

Bock-Hennig, Barbara S; Kohle, Christoph; Nill, Karl; Bock, Karl Walter

2002-01-15

203

Synergistic Action of Fibroblast Growth Factor-2 and Transforming Growth Factor-beta1 Enhances Bioprinted Human Neocartilage Formation  

PubMed Central

Bioprinting as a promising but unexplored approach for cartilage tissue engineering has the advantages of high throughput, digital control, and highly accurate placement of cells and biomaterial scaffold to the targeted 3D locations with simultaneous polymerization. This study tested feasibility of using bioprinting for cartilage engineering and examined the influence of cell density, growth and differentiation factors. Human articular chondrocytes were printed at various densities, stimulated transiently with growth factors and subsequently with chondrogenic factors. Samples were cultured for up to 4 weeks to evaluate cell proliferation and viability, mechanical properties, mass swelling ratio, water content, gene expression, ECM production, DNA content, and histology. Bioprinted samples treated with FGF-2/TGF-?1 had the best chondrogenic properties among all groups apparently due to synergistic stimulation of cell proliferation and chondrogenic phenotype. ECM production per chondrocyte in low cell density was much higher than that in high cell seeding density. This finding was also verified by mechanical testing and histology. In conclusion, cell seeding density that is feasible for bioprinting also appears optimal for human neocartilage formation when combined with appropriate growth and differentiation factors. PMID:22508498

Cui, Xiaofeng; Breitenkamp, Kurt; Lotz, Martin; D'Lima, Darryl

2012-01-01

204

Pinch sheets and reconnection in astrophysics  

Microsoft Academic Search

Magnetic reconnection processes involving the formation and destruction of pinch current sheets in plasma are a universal phenomenon typical of both laboratory and space plasmas. In current sheets a rapid dissipation of the magnetic field is possible in conditions of high conductivity and large scales of the plasma. This effect results from specific features of the flow near the null

S. I. Syrovatskii

1981-01-01

205

Effect of formation and state of interface on joint strength in friction stir spot welding for advanced high strength steel sheets  

NASA Astrophysics Data System (ADS)

The tensile shear strength and cross tension strength of friction stir spot welded joints were evaluated in the cases of lap joints of 270 N/mm2 grade and 980 N/mm2 grade cold rolled steel sheets with respect to the stir zone area, hardness distribution, and interface condition between the sheets. The results suggested that both the tensile shear strength and cross tension strength were based on the stir zone area and its hardness in both grades of steel. The "hook" shape of the interface also affected the joint strength. However, the joining that occurred across the interfaces had a significant influence on the value of the joint strength in the case of the 270 N/mm2 grade steel.

Taniguchi, Koichi; Matsushita, Muneo; Ikeda, Rinsei; Oi, Kenji

2014-08-01

206

Two-dimensional structure of {beta}-Amyloid(10-35) fibrils.  

SciTech Connect

{beta}-Amyloid (A{beta}) peptides are the main protein component of the pathognomonic plaques found in the brains of patients with Alzheimer's disease. These heterogeneous peptides adopt a highly organized fibril structure both in vivo and in vitro. Here we use solid-state NMR on stable, homogeneous fibrils of A{beta}{sub (10-35)}. Specific interpeptide distance constraints are determined with dipolar recoupling NMR on fibrils prepared from a series of singly labeled peptides containing {sup 13}C-carbonyl-enriched amino acids, and skipping no more than three residues in the sequence. From these studies, we demonstrate that the peptide adopts the structure of an extended parallel {beta}-sheet in-register at pH 7.4. Analysis of DRAWS data indicates interstrand distances of 5.3 {+-} 0.3 {angstrom} (mean {+-} standard deviation) throughout the entire length of the peptide, which is compatible only with a parallel {beta}-strand in-register. Intrastrand NMR constraints, obtained from peptides containing labels at two adjacent amino acids, confirm the secondary structural findings obtained using DRAWS. Using peptides with {sup 13}C incorporated at the carbonyl position of adjacent amino acids, structural transitions from {alpha}-helix to {beta}-sheet were observed at residues 19 and 20, but using similar techniques, no evidence for a turn could be found in the putative turn region comprising residues 25-29. Implications of this extended parallel organization for A{beta}{sub (10-35)} for overall fibril formation, stability, and morphology based upon specific amino acid contacts are discussed.

Benzinger, T. L. S.; Gregory, D. M.; Burkoth, T. S.; Miller-Auer, H.; Lynn, D. G.; Botto, R. E.; Meredith, S. C.; Chemistry; Univ. of Chicago

2000-03-28

207

Beta experiment  

NASA Technical Reports Server (NTRS)

A focused laser doppler velocimeter (LDV) system was developed for the measurement of atmospheric backscatter (beta) from aerosols at infrared wavelengths. A Doppler signal generator was used in mapping the coherent sensitive focal volume of a focused LDV system. System calibration data was analyzed during the flight test activity scheduled for the Beta system. These analyses were performed to determine the acceptability of the Beta measurement system's performance.

1982-01-01

208

Implantation of silicon dioxide-based nanocrystalline hydroxyapatite and pure phase beta-tricalciumphosphate bone substitute granules in caprine muscle tissue does not induce new bone formation  

PubMed Central

Background Osteoinductive bone substitutes are defined by their ability to induce new bone formation even at heterotopic implantation sites. The present study was designed to analyze the potential osteoinductivity of two different bone substitute materials in caprine muscle tissue. Materials and methods One gram each of either a porous beta-tricalcium phosphate (?-TCP) or an hydroxyapatite/silicon dioxide (HA/SiO2)-based nanocrystalline bone substitute material was implanted in several muscle pouches of goats. The biomaterials were explanted at 29, 91 and 181 days after implantation. Conventional histology and special histochemical stains were performed to detect osteoblast precursor cells as well as mineralized and unmineralized bone matrix. Results Both materials underwent cellular degradation in which tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like cells and TRAP-negative multinucleated giant cells were involved. The ß-TCP was completely resorbed within the observation period, whereas some granules of the HA-groups were still detectable after 180 days. Neither osteoblasts, osteoblast precursor cells nor extracellular bone matrix were found within the implantation bed of any of the analyzed biomaterials at any of the observed time points. Conclusions This study showed that ß-TCP underwent a faster degradation than the HA-based material. The lack of osteoinductivity for both materials might be due to their granular shape, as osteoinductivity in goat muscle has been mainly attributed to cylindrical or disc-shaped bone substitute materials. This hypothesis however requires further investigation to systematically analyze various materials with comparable characteristics in the same experimental setting. PMID:23286366

2013-01-01

209

MESSENGER and Venus Express Observations of the Near-tail of Venus: Magnetic Flux Transport, Current Sheet Structure, and Flux Rope Formation  

NASA Technical Reports Server (NTRS)

At 23:08 UT on 5 June 2007 the MESSENGER spacecraft reached its closest approach altitude (338 km) during its second flyby of Venus en route to its 2011 orbit insertion at Mercury. Whereas no measurements were collected during MESSENGER'S first Venus flyby in October 2006, the Magnetometer (MAG) and the Energetic Particle and Plasma Spectrometer (EPPS) operated successfully throughout this second encounter. Venus provides the solar system's best example to date of a solar wind - ionosphere planetary interaction. We present MESSENGER observations of the near-tail of Venus with emphasis on determining the time scales for magnetic flux transport, the structure of the cross-tail current sheet at very low altitudes (approx. 300 to 1000 km), and the nature and origin of a magnetic flux rope observed in the current sheet. The availability of the simultaneous Venus Express upstream measurements provides a unique opportunity to examine the influence of solar wind plasma and interplanetary magnetic field conditions on this planet's solar wind interaction at solar minimum.

Slavin, James A.; Boardsen, S. A.; Sarantos, M.; Acuna, M. H.; Anderson, B. J.; Barabash, S.; Benna, M.; Fraenz, M.; Gloeckler, G.; Gold, R. E.; Ho, G. C.; Korth, H.; Krimigis, S. M.; McNutt, R. L., Jr.; Raines, J. M.; Solomon, S. C.; Zhang, T.-L.; Zurbuchen, T. H.

2008-01-01

210

Elevated systemic TGF-beta impairs aortic vasomotor function through activation of NADPH oxidase-driven superoxide production and leads to hypertension, myocardial remodeling, and increased plaque formation in apoE(-/-) mice.  

PubMed

The role of circulating, systemic TGF-beta levels in endothelial function is not clear. TGF-beta(1) may cause endothelial dysfunction in apolipoprotein E-deficient (apoE(-/-)) mice via stimulation of reactive oxygen species (ROS) production by the NADPH oxidase (NOX) system and aggravate aortic and heart remodeling and hypertension. Thoracic aorta (TA) were isolated from 4-mo-old control (C57Bl/6), apoE(-/-), TGF-beta(1)-overexpressing (TGFbeta(1)), and crossbred apoE(-/-) x TGFbeta(1) mice. Endothelium-dependent relaxation was measured before and after incubation with apocynin (NOX inhibitor) or superoxide dismutase (SOD; ROS scavenger). Superoxide production within the vessel wall was determined by dihydroethidine staining under confocal microscope. In 8-mo-old mice, aortic and myocardial morphometric changes, plaque formation by en face fat staining, and blood pressure were determined. Serum TGF-beta(1) levels (ELISA) were elevated in TGFbeta(1) mice without downregulation of TGF-beta-I receptor (immunohistochemistry). In the aortic wall, superoxide production was enhanced and NO-dependent relaxation diminished in apoE(-/-) x TGFbeta(1) mice but improved significantly after apocynin or SOD. Myocardial capillary density was reduced, fibrocyte density increased, aortic wall was thicker, combined lesion area was greater, and blood pressure was higher in the apoE(-/-) x TGFbeta vs. C57Bl/6 mice. Our results demonstrate that elevated circulating TGF-beta(1) causes endothelial dysfunction through NOX activation-induced oxidative stress, accelerating atherosclerosis and hypertension in apoE(-/-) mice. These findings may provide a mechanism explaining accelerated atherosclerosis in patients with elevated plasma TGFbeta(1). PMID:20511416

Buday, Anna; Orsy, Petra; Godó, Mária; Mózes, Miklós; Kökény, Gábor; Lacza, Zsombor; Koller, Akos; Ungvári, Zoltán; Gross, Marie-Luise; Benyó, Zoltán; Hamar, Péter

2010-08-01

211

Beta Beams  

NASA Astrophysics Data System (ADS)

The ultimate goal of neutrino oscillation physics is the search for leptonic CP violation, which will require neutrino beams that are much more intense and pure than those used in present experiments. Beta beams are an attractive innovative possibility in this direction. Neutrinos are generated by the beta decays of radioactive nuclei and are accelerated at very high energies. The resulting neutrino beam consists of only one easily predictable flavor of neutrinos (ve or [Formula: see text]). A realistic beta beam design, which has already been demonstrated by the Eurisol Design Study, is based on CERN's PS and SPS accelerators. The beta beam concept has also been extended in several other directions, including high energy, high Q, electron capture, and low energy. Both the accelerator complex and the physics potential of a neutrino experiment are reviewed here. We emphasize the beta beam design based on the CERN PS and SPS, but we also discuss other possibilities.

Lindroos, Mats; Mezzetto, Mauro

2010-11-01

212

Kinetic Studies of Inhibition of the A?(1-42) Aggregation Using a Ferrocene-tagged ?-Sheet Breaker Peptide  

PubMed Central

The aggregation of amyloidogenic proteins/peptides has been closely linked to the neuropathology of several important neurological disorders. In Alzheimer's disease (AD), amyloid beta (A?) peptides and their aggregation are believed to be at least partially responsible for the etiology of AD. The aggregate-inflicted cellular toxicity can be inhibited by short peptides whose sequence are homologous to segments of the A?(1–42) peptide responsible for ?-sheet stacking (referred to as the ?-sheet breaker peptides). Herein a water-soluble ferrocene (Fc)-tagged ?-sheet breaker peptide (Fc-KLVFFK6) is used as an electrochemical probe for kinetic studies of the inhibition of the A?(1–42) fibrillation process and for determination of the optimal concentration of ?-sheet breaker peptide for efficient inhibition. Our results demonstrated that Fc-KLVFFK6 interacts with the A? aggregates instantaneously in solution, and sub-stoichiometric amount of Fc-KLVFFK6 is sufficient to inhibit the formation of the A? oligomers and fibrils and to reduce the toxicity of A?(1–42). The interaction between Fc-KLVFFK6 and A?(1–42) follows a pseudo-first-order reaction, with a rate constant of 1.89 ± 0.05 × 10?4 s?1. Tagging ?-sheet breaker peptides with a redox label facilitates design, screening, and rational use of peptidic inhibitors for impeding/altering A? aggregation. PMID:23232068

Zhang, Lin; Yagnik, Gargey; Peng, Yong; Wang, Jianxiu; Xu, H. Howard; Hao, Yuanqiang; Liu, You-Nian; Zhou, Feimeng

2013-01-01

213

Identification, classification, and analysis of beta-bulges in proteins.  

PubMed Central

A beta-bulge is a region of irregularity in a beta-sheet involving two beta-strands. It usually involves two or more residues in the bulged strand opposite to a single residue on the adjacent strand. These irregularities in beta-sheets were identified and classified automatically, extending the definition of beta-bulges given by Richardson et al. (Richardson, J.S., Getzoff, E.D., & Richardson, D.C., 1978, Proc. Natl. Acad. Sci. USA 75, 2574-2578). A set of 182 protein chains (170 proteins) was used, and a total of 362 bulges were extracted. Five types of beta-bulges were found: classic, G1, wide, bent, and special. Their characteristic amino acid preferences were found for most classes of bulges. Basically, bulges occur frequently in proteins; on average there are more than two bulges per protein. In general, beta-bulges produce two main changes in the structure of a beta-sheet: (1) disrupt the normal alternation of side-chain direction; (2) accentuate the twist of the sheet, altering the direction of the surrounding strands. PMID:8251933

Chan, A. W.; Hutchinson, E. G.; Harris, D.; Thornton, J. M.

1993-01-01

214

Coculture of peripheral blood CD34+ cell and mesenchymal stem cell sheets increase the formation of bone in calvarial critical-size defects in rabbits.  

PubMed

The reconstruction of large bony defects remains a clinical challenge, and angiogenesis and neovascularisation are being given more attention in bone tissue engineering. In this study we cocultured peripheral blood CD34+ cells (PB-CD34+ cells), an endothelial progenitor cell/haematopoietic stem cell-enriched population, with bone marrow-derived mesenchymal stem cells (MSC) to investigate their potential for bony regeneration. Cocultured cells showed better osteogenic differentiation than MSC alone in vitro. The cocultured cells and MSC sheets were also composited with hydroxyapatite and implanted in calvarial critical-size defects in rabbits. The rabbits were killed before microcomputed tomographic (MicroCT) and histological analysis. The results showed that cocultured cell composites had promoted bony regeneration more efficiently by 8 weeks after implantation. Our results indicate that the coculture of PB-CD34+ cells and MSC increases bony regeneration in calvarial critical-size defects in rabbits, and provide a new promising therapeutic strategy to aid skeletal healing. PMID:24210781

Li, Guanghui; Wang, Xi; Cao, Jian; Ju, Zhaoyu; Ma, Dongyang; Liu, Yanpu; Zhang, Junrui

2014-02-01

215

Gender-related effects of 17-{beta}-estradiol and B-hexachlorocyclohexane on liver tumor formation in medaka (Oryzias latipes)  

SciTech Connect

When medaka were acutely exposed to diethylnitrosamine (DEN), greater incidence of hepatocarcinoma was seen in female versus male fish. This is possibly related to elevated female endogenous estrogens, which increase liver weight and production of vitellogenin. To examine roles of estrogens in tumor modulation, 21-day old medaka were exposed to DEN (200 ppm for 24 hr.), then fed purified diets containing the estrogenic compound {beta}-hexachlorocyclohexane ({beta}-HCH) or 17-{beta}estradiol (E2) for 6 months. Incidences of basophilic preneoplastic foci of cellular alteration in females receiving DEN and 0.01, 0.1, or 1.0 ppm E2 were three times the incidences in similarly-treated males. Also, incidences of basophilic foci in DEN + 0.1 ppm E2 males were significantly increased over DEN-only males and were equal to incidences in DEN-only females. Liver weights and hepatosomatic indices of males given 0.1 ppm E2 were not significantly different than females fed control diet. Females fed 0.01-10.0 ppm {beta}-HCH after DEN had 4--5 times greater incidences of basophilic foci as males. Gender-related effects on kinetics of growth rates and volumes of foci are being examined.

Cooke, J.B.; Hinton, D.E. [Univ. of California, Davis, CA (United States)

1994-12-31

216

Note Sheets: A Reliable Predictor of Success?  

NSDL National Science Digital Library

Students in a large introductory-level biology course brought one page of notes to their exams. The authors scored these note sheets for their format and content. Student performance on exams showed a very limited correlation with the format or content of

White, Brian; Puopolo, Denise; Ceglie, Robert

2001-11-01

217

Rangeland Sheet 6 Soil Quality Information Sheet  

E-print Network

. Increasing levels of organic matter promote a higher water- holding capacity, which results in increasedRangeland Sheet 6 Soil Quality Information Sheet Rangeland Soil Quality--Organic Matter USDA, Natural Resources Conservation Service May 2001 Table 1.--Soil organic matter Component Rate of Primary

218

Antibacterial activities and conformations of bovine beta-defensin BNBD-12 and analogs:structural and disulfide bridge requirements for activity.  

PubMed

Structure and biological activities of synthetic peptides corresponding to bovine neutrophil beta-defensin BNBD-12, GPLSC(1)GRNGGVC(2)IPIRC(3) PVPMRQIGTC(4) FGRPVKC(5) C(6)RSW with disulfide connectivities C(1)-C(5), C(2)-C(4) and C(3)-C(6) and its variants with one, two and three disulfide bridges have been investigated. Selective protection of cysteine thiols was necessary in the four and six cysteine containing peptides for the formation of disulfide connectivities as observed in BNBD-12. Circular dichroism (CD) spectra indicate that in aqueous medium, only a small fraction of molecules populate turn-like conformations. In the presence of micelles and lipid vesicles, the single, two and three disulfide containing peptides adopt beta-hairpin or beta-sheet structures. Antibacterial activity was observed for all the peptides, irrespective of the number of disulfide bridges or how they were connected. Our results suggest that a rigid beta-sheet structure or the presence of three disulfide bridges does not appear to be stringent requirements for antibacterial activity in beta-defensins. PMID:11835989

Mandal, M; Jagannadham, M V; Nagaraj, R

2002-03-01

219

Spot welding of steel and aluminum using insert sheet  

SciTech Connect

Automobile industries have been increasingly interested in the use of aluminum and thus joining of steel and aluminum becomes of importance. The joining of the two types of metal raises a problem of brittle welds caused by the formation of intermetallic compounds. The authors solved the problem by using an insert sheet. This paper deals with the resistance spot welding of steel and aluminum sheets using insert sheets. The insert sheet used in the present development was a steel/aluminum clad sheet of the 0.8 mm thickness with 50% steel and 50% aluminum. The clad sheet was produced by warm rolling of steel and aluminum with a direct resistance heating process. Steel to be warm rolled was of EDDQ of the 0.4 mm thickness and aluminum was of JIS A1050 of 0.6 mm thickness. The mechanical properties of the insert clad sheets were in between those of the steel sheets and the aluminum sheets, while the clad sheets showed much better formability than the aluminum sheets. Resistance spot welding was conducted for 0.8 mm thick EDDQ steel sheets and 1.0 mm thick aluminum alloy (AL-5.5%Mg) sheets under the welding force of 1.96 kN, welding current ranging between 4.2 and 20.1 kA, and welding time from 0.5 to 10 cycles. The steel was spot welded to the steel side of the insert sheet while the aluminum was welded to the aluminum side. What the authors investigated were the applicable welding current range, nugget diameter, tensile shear strength, U-tension strength, and macro- and microstructures. In conclusion, steel sheets can be spot welded to aluminum sheets without difficulty by using clad sheets as insert materials while the strength level of the dissimilar metal spot welds is close to that of aluminum joints.

Oikawa, H.; Saito, T.; Yoshimura, T. [and others

1994-12-31

220

Thermoforming of foam sheet  

Microsoft Academic Search

Thermoforming is a widely used process for the manufacture of foam sheet products. Polystyrene foam food trays for instance can be produced by first heating the thermoplastic foam sheet, causing the gas contained to build up pressure and expand, after which a vacuum pressure can be applied to draw the sheet in the required form on the mould. This production

Remko Akkerman; Ruud M. Pronk

1997-01-01

221

In-situ time-of-flight neutron diffraction of ErD2 (beta phase) formation during D2 loading.  

SciTech Connect

In an effort to better understand the structural changes occurring during hydrogen loading of erbium target materials, we have performed D{sub 2} loading of erbium metal (powder) with simultaneous neutron diffraction analysis. This experiment tracked the conversion of Er metal to the {alpha} erbium deuteride (solid-solution) phase and then on to the {beta} (fluorite) phase. Complete conversion to ErD{sub 2.0} was accomplished at 10 Torr D{sub 2} pressure with deuterium fully occupying the tetrahedral sites in the fluorite lattice. Increased D{sub 2} pressure (up to 500 Torr at 450 C) revealed {approx}10 % deuterium occupation of the octahedral sites. Subsequent vacuum pumping of the sample at 450 C removed octahedral site occupancy while maintaining tetrahedral deuterium occupancy, thereby yielding stoichiometric ErD{sub 2.0} {beta} phase.

Browning, James Frederick (Oak Ridge National Laboratory, Oak Ridge, TN); Llobet, Anna (Los Alamos National Laboratory, Los Alamos, NM); Snow, Clark Sheldon; Rodriguez, Mark Andrew; Wixom, Ryan R.

2008-06-01

222

Formation of gamma'-Ni3Al via the Peritectoid Reaction: gamma plus beta (+Al2O3) equals gamma'(+Al2O3)  

NASA Technical Reports Server (NTRS)

The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8 - 32 at.%Al and temperature range T = 1400 - 1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma'-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3) = gamma + beta (+ Al2O3), at 1640 plus or minus 1 K and a liquid composition of 24.8 plus or minus 0.2 at.%Al (at an unknown oxygen content). The {gamma + beta + Al2O3} phase field is stable over the temperature range 1633 - 1640 K, and gamma'-Ni3Al forms via the peritectiod, gamma + beta (+ Al2O3) = gamma'(+ Al2O3), at 1633 plus or minus 1 K. This behavior is inconsistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma'-Ni3Al phase field.

Copland, Evan

2008-01-01

223

Formation of gamma(sup prime)-Ni3Al via the Peritectoid Reaction: gamma + beta (+ Al2O3)=gamma(sup prime)(+ Al2O3)  

NASA Technical Reports Server (NTRS)

The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8-32 at.%Al and temperature range T=1400-1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma(sup prime)-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3)=gamma + Beta(+ Al2O3), at 1640 +/- 1 K and a liquid composition of 24.8 +/- 0.2 at.%al (at an unknown oxygen content). The {gamma + Beta (+Al2O3} phase field is stable over the temperature range 1633-1640 K, and gamma(sup prime)-Ni3Al forms via the peritectoid, gamma + Beta (+ Al2O3)=gamma(sup prime) (+ Al2O3), at 1633 +/- 1 K. This behavior is consistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady-state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma(sup prime)-Ni2Al phase field.

Copeland, Evan

2008-01-01

224

THE DEPENDENCE OF MAGNETIC RECONNECTION ON PLASMA {beta} AND MAGNETIC SHEAR: EVIDENCE FROM SOLAR WIND OBSERVATIONS  

SciTech Connect

We address the conditions for the onset of magnetic reconnection based on a survey of 197 reconnection events in solar wind current sheets observed by the Wind spacecraft. We report the first observational evidence for the dependence of the occurrence of reconnection on a combination of the magnetic field shear angle, {theta}, across the current sheet and the difference in the plasma {beta} values on the two sides of the current sheet, {Delta}{beta}. For low {Delta}{beta}, reconnection occurred for both low and high magnetic shears, whereas only large magnetic shear events were observed for large {Delta}{beta}: Events with shears as low as 11{sup 0} were observed for {Delta}{beta} < 0.1, but for {Delta}{beta} > 1.5 only events with {theta} > 100{sup 0} were detected. Our observations are in quantitative agreement with a theoretical prediction that reconnection is suppressed in high {beta} plasmas at low magnetic shears due to super-Alfvenic drift of the X-line caused by plasma pressure gradients across the current sheet. The magnetic shear-{Delta}{beta} dependence could account for the high occurrence rate of reconnection observed in current sheets embedded within interplanetary coronal mass ejections, compared to those in the ambient solar wind. It would also suggest that reconnection could occur at a substantially higher rate in solar wind current sheets closer to the Sun than at 1 AU and thus may play an important role in the generation and heating of the solar wind.

Phan, T. D.; Pasma, C.; Oeieroset, M.; Larson, D.; Lin, R. P.; Davis, M. S. [SSL, University of California, Berkeley, CA 94720 (United States); Gosling, J. T. [University of Colorado, Boulder, CO (United States); Paschmann, G. [MPE, Garching (Germany); Drake, J. F., E-mail: phan@ssl.berkeley.ed [University of Maryland, College Park, MD (United States)

2010-08-20

225

Vertical displacements of the current sheet and Hall currents  

NASA Astrophysics Data System (ADS)

Vertical displacements of the peripheral regions of the current sheet with respect to its mean plane have been detected in the case of the sheet formation in the three-dimensional configuration with the X line and longitudinal component of the magnetic field. It has been shown that this effect is due to the generation of Hall currents and the appearance of vertically directed forces. Change in the sign of vertical displacements at the late stage of the sheet evolution has been detected, indicating the generation of opposite Hall currents when the direction of the main current near the side edges of the sheet changes. It has been shown that Hall currents significantly affect the structure of current sheets, and vertical oscillations of the peripheral regions of the current sheet, which appear owing to oppositely directed Hall currents, are involved in the dynamic processes in current sheets.

Frank, A. G.; Satunin, S. N.

2014-09-01

226

The iA{beta}5p {beta}-breaker peptide regulates the A{beta}(25-35) interaction with lipid bilayers through a cholesterol-mediated mechanism  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer iA{beta}5p shows a significant tendency to deeply penetrates the hydrophobic core of lipid membrane. Black-Right-Pointing-Pointer A{beta}(25-35) locates in the external region of the membrane causing a re-positioning of CHOL. Black-Right-Pointing-Pointer iA{beta}5p withholds cholesterol in the inner hydrophobic core of the lipid membrane. Black-Right-Pointing-Pointer iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane. -- Abstract: Alzheimer's disease is characterized by the deposition of aggregates of the {beta}-amyloid peptide (A{beta}) in the brain. A potential therapeutic strategy for Alzheimer's disease is the use of synthetic {beta}-sheet breaker peptides, which are capable of binding A{beta} but unable to become part of a {beta}-sheet structure, thus inhibiting the peptide aggregation. Many studies suggest that membranes play a key role in the A{beta} aggregation; consequently, it is strategic to investigate the interplay between {beta}-sheet breaker peptides and A{beta} in the presence of lipid bilayers. In this work, we focused on the effect of the {beta}-sheet breaker peptide acetyl-LPFFD-amide, iA{beta}5p, on the interaction of the A{beta}(25-35) fragment with lipid membranes, studied by Electron Spin Resonance spectroscopy, using spin-labeled membrane components (either phospholipids or cholesterol). The ESR results show that iA{beta}5p influences the A{beta}(25-35) interaction with the bilayer through a cholesterol-mediated mechanism: iA{beta}5p withholds cholesterol in the inner hydrophobic core of the bilayer, making the interfacial region more fluid and capable to accommodate A{beta}(25-35). As a consequence, iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane, which is the first step of the {beta}-amyloid aggregation process.

Vitiello, Giuseppe [Department of Chemistry, University of Naples 'Federico II', Naples (Italy) [Department of Chemistry, University of Naples 'Federico II', Naples (Italy); CSGI (Consorzio per lo Sviluppo dei Sistemi a Grande Interfase), Florence (Italy)] [Consorzio per lo Sviluppo dei Sistemi a Grande Interfase; Italy; Grimaldi, Manuela; D'Ursi, Anna Maria [Department of Pharmaceutical Science, University of Salerno, Fisciano (Italy)] [Department of Pharmaceutical Science, University of Salerno, Fisciano (Italy); D'Errico, Gerardino, E-mail: gerardino.derrico@unina.it [Department of Chemistry, University of Naples 'Federico II', Naples (Italy) [Department of Chemistry, University of Naples 'Federico II', Naples (Italy); CSGI (Consorzio per lo Sviluppo dei Sistemi a Grande Interfase), Florence (Italy)] [Consorzio per lo Sviluppo dei Sistemi a Grande Interfase; Italy

2012-01-06

227

Beta titanium alloys in the 80's; Proceedings of the Symposium, Atlanta, GA, March 8, 1983  

Microsoft Academic Search

Among the topics discussed are the use of beta-Ti in the SR-71 aircraft, the microstructure and properties of beta-Ti alloys, the effects of hydrogen, heat treatment, and omega-phase formation on beta-Ti, the primary processing of beta- and near-beta-Ti alloys, the processing window for grain size control in metastable beta-Ti, grain growth in beta III-Ti, the processing and properties of Ti-17

R. R. Boyer; H. W. Rosenberg

1984-01-01

228

Chronic lithium administration to FTDP-17 tau and GSK-3beta overexpressing mice prevents tau hyperphosphorylation and neurofibrillary tangle formation, but pre-formed neurofibrillary tangles do not revert.  

PubMed

Glycogen synthase kinase-3 (GSK-3) has been proposed as the main kinase able to aberrantly phosphorylate tau in Alzheimer's disease (AD) and related tauopathies, raising the possibility of designing novel therapeutic interventions for AD based on GSK-3 inhibition. Lithium, a widely used drug for affective disorders, inhibits GSK-3 at therapeutically relevant concentrations. Therefore, it was of great interest to test the possible protective effects of lithium in an AD animal model based on GSK-3 overexpression. We had previously generated a double transgenic model, overexpressing GSK-3beta in a conditional manner, using the Tet-off system and tau protein carrying a triple FTDP-17 (frontotemporal dementia and parkinsonism linked to chromosome 17) mutation. This transgenic line shows tau hyperphosphorylation in hippocampal neurones accompanied by neurofibrillary tangles (NFTs). We used this transgenic model to address two issues: first, whether chronic lithium treatment is able to prevent the formation of aberrant tau aggregates that result from the overexpression of FTDP-17 tau and GSK-3beta; second, whether lithium is able to change back already formed NFTs in aged animals. Our data suggest that progression of the tauopathy can be prevented by administration of lithium when the first signs of neuropathology appear. Furthermore, it is still possible to partially reverse tau pathology in advanced stages of the disease, although NFT-like structures cannot be changed. The same results were obtained after shut-down of GSK-3beta overexpression, supporting the possibility that GSK-3 inhibition is not sufficient to reverse NFT-like aggregates. PMID:17059563

Engel, Tobias; Goñi-Oliver, Paloma; Lucas, José J; Avila, Jesús; Hernández, Félix

2006-12-01

229

What factor drives the fibrillogenic association of ?-sheets?  

Microsoft Academic Search

The identification of the driving factor for fibril formation is paramount to understand the molecular basis of amyloidogenic disease. Recently, an atomic-detail structure of a fibrillogenic aggregate was reported and revealed a tight packing of ?-sheets. However, there is not a single pair-wise interaction of significance between the ?-sheets, no hydrogen bond and no hydrophobic interaction. Instead, there is extensive

Ariel Fernández

2005-01-01

230

Dynamic Formation of a Hot Field Reversed Configuration with Improved Confinement by Supersonic Merging of Two Colliding High-{beta} Compact Toroids  

SciTech Connect

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-{beta} plasmoids preformed by the dynamic version of field-reversed {theta}-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{sub i}+T{sub e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

Binderbauer, M. W.; Guo, H. Y.; Tuszewski, M.; Putvinski, S.; Sevier, L.; Barnes, D.; Rostoker, N.; Anderson, M. G.; Andow, R.; Bonelli, L.; Brown, R.; Bui, D. Q.; Bystritskii, V.; Clary, R.; Cheung, A. H.; Conroy, K. D.; Deng, B. H.; Dettrick, S. A.; Douglass, J. D.; Feng, P. [Tri Alpha Energy, Inc., Post Office Box 7010, Rancho Santa Margarita, California 92688 (United States)

2010-07-23

231

Material Safety Data Sheets  

E-print Network

What the Material Safety Data Sheet (MSDS) tells you: The MSDS provides you with the information you need to know to protect yourself from exposure to a particular hazardous chemical, under normal conditions of use, as well as during emergencies. The information on an MSDS is provided by the manufacturer or distributor of the chemical. You are required by OSHA to maintain copies of the MSDSs for the chemicals used and stored in your work area. Regulations do not require a standard format for MSDS information, so one MSDS may look different than another. However, regulations do require that all MSDSs be written in English and that they provide the following information: n Chemical name, trade name, synonyms and CAS number n Name, address and telephone number of the manufacturer n List of hazardous ingredients n Exposure limits (OSHA PELs, ACGIH TLVs or other established limits) n Conditions under which the chemical will burn, explode, melt or become a dangerous gas n Normal appearance and odor of the chemical n How to put out a fire involving the chemical

Quick Reference

232

Synthesis of nanometre-thick MoO3 sheets.  

PubMed

The formation of MoO(3) sheets of nanoscale thickness is described. They are made from several fundamental sheets of orthorhombic alpha-MoO(3), which can be processed in large quantities via a low cost synthesis route that combines thermal evaporation and mechanical exfoliation. These fundamental sheets consist of double-layers of linked distorted MoO(6) octahedra. Atomic force microscopy (AFM) measurements show that the minimum resolvable thickness of these sheets is 1.4 nm which is equivalent to the thickness of two double-layers within one unit cell of the alpha-MoO(3) crystal. PMID:20644828

Kalantar-zadeh, Kourosh; Tang, Jianshi; Wang, Minsheng; Wang, Kang L; Shailos, Alexandros; Galatsis, Kosmas; Kojima, Robert; Strong, Veronica; Lech, Andrew; Wlodarski, Wojtek; Kaner, Richard B

2010-03-01

233

Emittance Measurements for a Thin Liquid Sheet Flow  

NASA Technical Reports Server (NTRS)

The Liquid Sheet Radiator (LSR) is an external flow radiator that uses a triangular-shaped flowing liquid sheet as the radiating surface. It has potentially much lower mass than solid wall radiators such as pumped loop and heat pipe radiators, along with being nearly immune to micrometeoroid penetration. The LSR has an added advantage of simplicity. Surface tension causes a thin (100-300 microns) liquid sheet to coalesce to a point, causing the sheet flow to have a triangular shape. Such a triangular sheet is desirable since it allows for simple collection of the flow at a single point. A major problem for all external flow radiators is the requirement that the working fluid be of very low (approx. 10(sup -8) torr) vapor pressure to keep evaporative losses low. As a result, working fluids are limited to certain oils (such as used in diffusion pumps) for low temperatures (300-400 K) and liquid metals for higher temperatures. Previous research on the LSR has been directed at understanding the fluid mechanics of thin sheet flows and assessing the stability of such flows, especially with regard to the formation of holes in the sheet. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. The latest research has been directed at determining the emittance of thin sheet flows. The emittance was calculated from spectral transmittance data for the Dow Corning 705 silicone oil. By experimentally setting up a sheet flow, the emittance was also determined as a function of measurable quantities, most importantly, the temperature drop between the top of the sheet and the temperature at the coalescence point of the sheet. Temperature fluctuations upstream of the liquid sheet were a potential problem in the analysis and were investigated.

Englehart, Amy N.; McConley, Marc W.; Chubb, Donald L.

1996-01-01

234

Synthesis of cyclic thioethers through tandem C(sp3)-S and C(sp2)-S bond formations from alpha,beta'-dichloro vinyl ketones.  

PubMed

The synthesis of 5- to 8-memebered cyclic thioethers 4 has been achieved through a simple two-step sequence. The present methodology utilizes the facile Friedel-Crafts acylation of terminal alkynes 1 with acid chlorides 2 followed by tandem C(sp(3))-S and C(sp(2))-S bond formations with NaSH.xH(2)O. PMID:18278938

Oh, Kyungsoo; Kim, Hyunjung; Cardelli, Francesco; Bwititi, Tamayi; Martynow, Anna M

2008-03-21

235

Interhemispheric ice-sheet synchronicity during the last glacial maximum  

USGS Publications Warehouse

The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere ice sheets. Surface climate forcing of Antarctic mass balance would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere ice sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric ice sheets.

Weber, M. E.; Clark, P. U.; Ricken, W.; Mitrovica, J. X.; Hostetler, S. W.; Kuhn, G.

2011-01-01

236

Interhemispheric ice-sheet synchronicity during the Last Glacial Maximum.  

PubMed

The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere ice sheets. Surface climate forcing of Antarctic mass balance would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere ice sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric ice sheets. PMID:22144623

Weber, Michael E; Clark, Peter U; Ricken, Werner; Mitrovica, Jerry X; Hostetler, Steven W; Kuhn, Gerhard

2011-12-01

237

Nuclear Data Sheets for A = 193  

SciTech Connect

The present revision of the properties for the nuclides belonging to the A = 193 mass chain contains many improvements, corrections and additions to the material presented in previous evaluations (1998Ar07, Nucl. Data Sheets 83, 921 (1998); 1990Sh30, Nucl, Data Sheets 61, 519 (1990)). Among these are measurement results for quadrupole moments, angular distribution coefficients, half-lives and g-factors, for both previously known and new transitions and levels. In addition, major changes to the previously known status of this mass chain consist in the inclusion of data for new superdeformed bands in {sup 193}Pb, and the creation of level schemes for {sup 193}Bi, {sup 193}Po and {sup 193}At. The latter were previously unavailable, except for a very limited attempt in the case of {sup 193}Po, which was not confirmed in later work. Furthermore, the {sup 193}Os beta decay was re-evaluated in order to account for new absolute intensity measurements.

Achterberg, E. [Laboratorio TANDAR, Departamento de Fisica, Comision Nacional de Energia Atomica, Buenos Aires (Argentina); Capurro, O.A. [Laboratorio TANDAR, Departamento de Fisica, Comision Nacional de Energia Atomica, Buenos Aires (Argentina); Marti, G.V. [Laboratorio TANDAR, Departamento de Fisica, Comision Nacional de Energia Atomica, Buenos Aires (Argentina); Vanin, V.R. [Lab. do Acelerador Linear, Universidade de San Paulo, Sao Paulo, SP (Brazil); Castro, R.M. [Lab. do Acelerador Linear, Universidade de San Paulo, Sao Paulo, SP (Brazil); Instituto de Estudos Avancados - IEAv, Centro Tecnico Aerospacial - CTA, Sao Jose dos Campos, SP (Brazil)

2006-01-15

238

Dynamics of beta-cell turnover: evidence for beta-cell turnover and regeneration from sources of beta-cells other than beta-cell replication in the HIP rat.  

PubMed

Type 2 diabetes is characterized by hyperglycemia, a deficit in beta-cells, increased beta-cell apoptosis, and islet amyloid derived from islet amyloid polypeptide (IAPP). These characteristics are recapitulated in the human IAPP transgenic (HIP) rat. We developed a mathematical model to quantify beta-cell turnover and applied it to nondiabetic wild type (WT) vs. HIP rats from age 2 days to 10 mo to establish 1) whether beta-cell formation is derived exclusively from beta-cell replication, or whether other sources of beta-cells (OSB) are present, and 2) to what extent, if any, there is attempted beta-cell regeneration in the HIP rat and if this is through beta-cell replication or OSB. We conclude that formation and maintenance of adult beta-cells depends largely ( approximately 80%) on formation of beta-cells independent from beta-cell duplication. Moreover, this source adaptively increases in the HIP rat, implying attempted beta-cell regeneration that substantially slows loss of beta-cell mass. PMID:19470833

Manesso, Erica; Toffolo, Gianna M; Saisho, Yoshifumi; Butler, Alexandra E; Matveyenko, Aleksey V; Cobelli, Claudio; Butler, Peter C

2009-08-01

239

Beta Thalassemia (For Parents)  

MedlinePLUS

... beta globin When the gene that controls the production of either of these proteins is missing or ... thalassemia occurs when the gene that controls the production of beta globin is defective. Beta thalassemia can ...

240

Modeling ice sheet permafrost interaction around the southern Laurentide Ice Sheet  

NASA Astrophysics Data System (ADS)

The existence of permanently frozen ground has a major influence on the dynamics of an advancing ice sheet and the formation of landforms. Cooling early in a glacial cycle produced extensive permafrost. The insulation effect of the ice sheet after advancing over areas of permafrost led to a slow degradation of permafrost under the ice. Finally, warming after the LGM casued the disappearence of subglacial premafrost. Subglacial permafrost affects directly the evolution of basal temperature and subglacial hydrology, both critical conditions for formation of landforms and fast flow instabilities. Surge-type flow instabilities may account for the relatively thin ice lobes, the dominant features around the southern margin of the Laurentide Ice Sheet (LIS). Numerical experiments of the last glacial cycle of the southern LIS were performed with a permafrost model of the earth's crust coupled with the three-dimensional thermomechanical UBC ice sheet model. This ice sheet model contains thickness evolution, ice flow, temperature evolution, and isostasy. The permafrost growth and decay is modeled solving the heat-transport equation for a mixture of sediment and bedrock with varying water and ice content. The transient permafrost condition beneath and peripheral to the ice sheet was analyzed for the last glacial maximum and the transition period to present climate.

Bauder, A.; Mickelson, D. M.; Marshall, S. J.

2003-04-01

241

Beta-diketiminate-stabilized magnesium(I) dimers and magnesium(II) hydride complexes: synthesis, characterization, adduct formation, and reactivity studies.  

PubMed

The preparation and characterization of a series of magnesium(II) iodide complexes incorporating beta-diketiminate ligands of varying steric bulk and denticity, namely, [(ArNCMe)(2)CH](-) (Ar=phenyl, ((Ph)Nacnac), mesityl ((Mes)Nacnac), or 2,6-diisopropylphenyl (Dipp, (Dipp)Nacnac)), [(DippNCtBu)(2)CH](-) ((tBu)Nacnac), and [(DippNCMe)(Me(2)NCH(2)CH(2)NCMe)CH](-) ((Dmeda)Nacnac) are reported. The complexes [((Ph)Nacnac)MgI(OEt(2))], [((Mes)Nacnac)MgI(OEt(2))], [((Dmeda)Nacnac)MgI(OEt(2))], [((Mes)Nacnac)MgI(thf)], [((Dipp)Nacnac)MgI(thf)], [((tBu)Nacnac)MgI], and [((tBu)Nacnac)MgI(DMAP)] (DMAP=4-dimethylaminopyridine) were shown to be monomeric by X-ray crystallography. In addition, the related beta-diketiminato beryllium and calcium iodide complexes, [((Mes)Nacnac)BeI] and [{((Dipp)Nacnac)CaI(OEt(2))}(2)] were prepared and crystallographically characterized. The reductions of all metal(II) iodide complexes by using various reagents were attempted. In two cases these reactions led to the magnesium(I) dimers, [((Mes)Nacnac)MgMg((Mes)Nacnac)] and [((tBu)Nacnac)MgMg((tBu)Nacnac)]. The reduction of a 1:1 mixture of [((Dipp)Nacnac)MgI(OEt(2))] and [((Mes)Nacnac)MgI(OEt(2))] with potassium gave a low yield of the crystallographically characterized complex [((Dipp)Nacnac)Mg(mu-H)(mu-I)Mg((Mes)Nacnac)]. All attempts to form beryllium(I) or calcium(I) dimers by reductions of [((Mes)Nacnac)BeI], [{((Dipp)Nacnac)CaI(OEt(2))}(2)], or [{((tBu)Nacnac)CaI(thf)}(2)] have so far been unsuccessful. The further reactivity of the magnesium(I) complexes [((Mes)Nacnac)MgMg((Mes)Nacnac)] and [((tBu)Nacnac)MgMg((tBu)Nacnac)] towards a variety of Lewis bases and unsaturated organic substrates was explored. These studies led to the complexes [((Mes)Nacnac)Mg(L)Mg(L)((Mes)Nacnac)] (L=THF or DMAP), [((Mes)Nacnac)Mg(mu-AdN(6)Ad)Mg((Mes)Nacnac)] (Ad=1-adamantyl), [((tBu)Nacnac)Mg(mu-AdN(6)Ad)Mg((tBu)Nacnac)], and [((Mes)Nacnac)Mg(mu-tBu(2)N(2)C(2)O(2))Mg((Mes)Nacnac)] and revealed that, in general, the reactivity of the magnesium(I) dimers is inversely proportional to their steric bulk. The preparation and characterization of [((tBu)Nacnac)Mg(mu-H)(2)Mg((tBu)Nacnac)] has shown the compound to have different structural and physical properties to [((tBu)Nacnac)MgMg((tBu)Nacnac)]. Treatment of the former with DMAP has given [((tBu)Nacnac)Mg(H)(DMAP)], the X-ray crystal structure of which disclosed it to be the first structurally authenticated terminal magnesium hydride complex. Although attempts to prepare [((Mes)Nacnac)Mg(mu-H)(2)Mg((Mes)Nacnac)] were not successful, a neutron diffraction study of the corresponding magnesium(I) complex, [((Mes)Nacnac)MgMg((Mes)Nacnac)] confirmed that the compound is devoid of hydride ligands. PMID:19950340

Bonyhady, Simon J; Jones, Cameron; Nembenna, Sharanappa; Stasch, Andreas; Edwards, Alison J; McIntyre, Garry J

2010-01-18

242

State Climate Change Impacts Information Sheets  

NSDL National Science Digital Library

The Environmental Protection Agency's (EPA) Global Warming site (discussed in the February 21, 1997 Scout Report) has placed all 50 state-specific global warming sheets online in HTML and .pdf format. Browseable via a clickable map or alphabetically, the sheets summarize expected climate change in each state and explain the projected consequences on factors such as health, agriculture, water resources, ecosystems, forests, and coastal areas. Brief countrywide overviews of these factors are also available, as well as short discussions of climate change and fisheries, birds, and national parks. Additional resources include a bibliography, glossary, and internal search engine.

1997-01-01

243

The use of beta titanium alloys in the aerospace industry  

Microsoft Academic Search

Beta titanium alloys have been available since the 1950s (Ti-13V-11Cr-3Mo or B120VCA), but significant applications of these alloys, beyond the SR-71 Blackbird, have been slow in coming. The next significant usage of a beta alloy did not occur until the mid-1980s on the B-1B bomber. This aircraft used Ti-15V-3Cr-3Al-3Sn sheet due to its capability for strip rolling, improved formability, and

R. R. Boyer; R. D. Briggs

2005-01-01

244

In silico and in vitro studies to elucidate the role of Cu2+ and galanthamine as the limiting step in the amyloid beta (1-42) fibrillation process.  

PubMed

The formation of fibrils and oligomers of amyloid beta (A?) with 42 amino acid residues (A? 1-42 ) is the most important pathophysiological event associated with Alzheimer's disease (AD). The formation of A? fibrils and oligomers requires a conformational change from an ?-helix to a ?-sheet conformation, which is encouraged by the formation of a salt bridge between Asp 23 or Glu 22 and Lys 28. Recently, Cu(2+) and various drugs used for AD treatment, such as galanthamine (Reminyl(®) ), have been reported to inhibit the formation of A? fibrils. However, the mechanism of this inhibition remains unclear. Therefore, the aim of this work was to explore how Cu(2+) and galanthamine prevent the formation of A?1-42 fibrils using molecular dynamics (MD) simulations (20 ns) and in vitro studies using fluorescence and circular dichroism (CD) spectroscopies. The MD simulations revealed that A?1-42 acquires a characteristic U-shape before the ?-helix to ?-sheet conformational change. The formation of a salt bridge between Asp 23 and Lys 28 was also observed beginning at 5 ns. However, the MD simulations of A? 1-42 in the presence of Cu(2+) or galanthamine demonstrated that both ligands prevent the formation of the salt bridge by either binding to Glu 22 and Asp 23 (Cu(2+) ) or to Lys 28 (galanthamine), which prevents A? 1-42 from adopting the U-characteristic conformation that allows the amino acids to transition to a ?-sheet conformation. The docking results revealed that the conformation obtained by the MD simulation of a monomer from the 1Z0Q structure can form similar interactions to those obtained from the 2BGE structure in the oligomers. The in vitro studies demonstrated that A? remains in an unfolded conformation when Cu(2+) and galanthamine are used. Then, ligands that bind Asp 23 or Glu 22 and Lys 28 could therefore be used to prevent ? turn formation and, consequently, the formation of A? fibrils. PMID:23904252

Hernández-Rodríguez, Maricarmen; Correa-Basurto, José; Benitez-Cardoza, Claudia G; Resendiz-Albor, Aldo Arturo; Rosales-Hernández, Martha C

2013-10-01

245

Dietary Supplement Fact Sheets  

MedlinePLUS

... print | view as pdf | share Create PDF Dietary Supplement Fact Sheets A - E | F - L | M - S | T - Z General Supplement Information Dietary Supplements: Background Information Botanical Dietary Supplements: ...

246

Avian Fact Sheet  

SciTech Connect

OAK-B135 After conducting four national research meetings, producing a document guiding research: Metrics and Methods for Determining or Monitoring Potential Impacts on Birds at Existing and Proposed Wind Energy Sites, 1999, and another paper, Avian Collisions with Wind Turbines: A Summary of Existing Studies and Comparisons to Other Sources of Avian Collision Mortality in the United States, 2001, the subcommittee recognized a need to summarize in a short fact sheet what is known about avian-wind interaction and what questions remain. This fact sheet attempts to summarize in lay terms the result of extensive discussion about avian-wind interaction on land. This fact sheet does not address research conducted on offshore development. This fact sheet is not intended as a conclusion on the subject; rather, it is a summary as of Fall/Winter 2002.

NWCC Wildlife Work Group

2004-12-01

247

Fact Sheet HEALTH SCIENCE  

E-print Network

Fact Sheet HEALTH SCIENCE Highlights · Health Science is the multidisciplinary study of the factors that influence health across the life course to health for all. · Health Science majors learn in the classroom

Su, Xiao

248

Global ice sheet modeling  

SciTech Connect

The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed.

Hughes, T.J.; Fastook, J.L. [Univ. of Maine, Orono, ME (United States). Institute for Quaternary Studies

1994-05-01

249

Monoatomically thin polarizable sheets  

E-print Network

We consider a flat lattice of dipoles modeled by harmonic oscillators interacting with the electromagnetic field in dipole approximation. Eliminating the variables from the coupled equations of motion, we come to effective Maxwell equations. These allow for taking the lattice spacing $a$ to zero. As a result, we obtain reflection coefficients for the scattering of electromagnetic waves off the sheet. These are a generalization of that known from the hydrodynamic model. For instance, we get a non trivial scattering for polarizability perpendicular to the sheet. Also we show that the case of a sheet polarizable parallel to the sheet can be obtained in a natural way from a plasma layer of finite thickness. As an alternative approach we discuss the elimination of the electromagnetic fields resulting in effective equations for the oscillators. These show, for $a\\to 0$, divergent behavior, resulting from the electrostatic interaction of the dipoles.

M. Bordag

2014-04-18

250

ERRATA SHEET ENVIRONMENTAL ASSESSMENT,  

E-print Network

alternatives for the Environmental Impact Statement for Essential Fish Habitat Identification and ConservationERRATA SHEET ENVIRONMENTAL ASSESSMENT, REGULATORY IMPACT REVIEW, AND REGULATORY FLEXIBILITY of Particular Concern April 2006 Note to Reviewers: The Environmental Assessment / Regulatory Impact Review

251

Cholesterol biosynthesis pathway intermediates and inhibitors regulate glucose-stimulated insulin secretion and secretory granule formation in pancreatic beta-cells.  

PubMed

Cholesterol is reportedly abundant in the endocrine secretory granule (SG) membrane. In this study, we examined the involvement of cholesterol biosynthesis intermediates and inhibitors in insulin secretion and SG formation mechanisms. There are two routes for the supply of cholesterol to the cells: one via de novo biosynthesis and the other via low-density lipoprotein receptor-mediated endocytosis. We found that insulin secretion and content are diminished by ?-hydroxy-?-methylglutaryl-coenzyme A inhibitor lovastatin but not by lipoprotein depletion from the culture medium in MIN6 ?-cells. Cholesterol biosynthesis intermediates mevalonate, squalene, and geranylgeranyl pyrophosphate enhanced glucose-stimulated insulin secretion, and the former two increased insulin content. The glucose-stimulated insulin secretion-enhancing effect of geranylgeranyl pyrophosphate was also confirmed in perifusion with rat islets. Morphologically, mevalonate and squalene increased the population of SGs without affecting their size. In contrast, lovastatin increased the SG size with reduction of insulin-accumulating dense cores, leading to a decrease in insulin content. Furthermore, insulin was secreted in a constitutive manner, indicating disruption of regulated insulin secretion. Because secretogranin III, a cholesterol-binding SG-residential granin-family protein, coincides with SG localization based on the cholesterol composition, secretogranin III may be associated with insulin-accumulating mechanisms. Although the SG membrane exhibits a high cholesterol composition, we could not find detergent-resistant membrane regions using a lipid raft-residential protein flotillin and a fluorescent cholesterol-Si-pyrene probe as markers on a sucrose-density gradient fractionation. We suggest that the high cholesterol composition of SG membrane with 40-50 mol% is crucial for insulin secretion and SG formation functions. PMID:20685866

Tsuchiya, Miho; Hosaka, Masahiro; Moriguchi, Tomohisa; Zhang, Shaojuan; Suda, Masayuki; Yokota-Hashimoto, Hiromi; Shinozuka, Kazuo; Takeuchi, Toshiyuki

2010-10-01

252

The thermographic nondestructive evaluation of iron aluminide green sheet  

NASA Astrophysics Data System (ADS)

The recent development of manufacturing techniques for the fabrication of thin iron aluminide sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet by cold rolling FeAl powder mixed with organic binding agents. The green sheet composite has a bulk density, which is typically less than about 3.6 g/cc. The finished sheet, with a density of about 6.1 g/cc, is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. The production environment and physical characteristics of the composite provide for unique challenges in developing a rapid nondestructive inspection capability. The method must be non-contact due to the fragile nature of the composite. Limited access to the material also demands a one-sided inspection technique. An active thermographic method providing for 100% on-line inspection within an industrial, process has been developed. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The mechanism of flaw formation and the transformation of green sheet flaws into defects that appear in intermediate and finished sheet products are described. A mathematical model which describes the green sheet heat transfer propagation, in the context of the inspection technique and the compact heterogeneity, is also presented. The potential for feedback within the production process is also discussed.

Watkins, Michael Lee

253

Dynamics of dikes versus cone sheets in volcanic systems  

NASA Astrophysics Data System (ADS)

sheet intrusions of various shapes, such as dikes and cone sheets, coexist as parts of complex volcanic plumbing systems likely fed by common sources. How they form is fundamental regarding volcanic hazards, yet no dynamic model simulates and predicts satisfactorily their diversity. Here we present scaled laboratory experiments that reproduced dikes and cone sheets under controlled conditions. Our models show that their formation is governed by a dimensionless ratio (?1), which describes the geometry of the magma source, and a dynamic dimensionless ratio (?2), which compares the viscous stresses in the flowing magma to the host rock strength. Plotting our experiments against these two numbers results in a phase diagram evidencing a dike and a cone sheet field, separated by a sharp transition that fits a power law. This result shows that dikes and cone sheets correspond to distinct physical regimes of magma emplacement in the crust. For a given host rock strength, cone sheets preferentially form when the source is shallow, relative to its lateral extent, or when the magma influx velocity (or viscosity) is high. Conversely, dikes form when the source is deep compared to its size, or when magma influx rate (or viscosity) is low. Both dikes and cone sheets may form from the same source, the shift from one regime to the other being then controlled by magma dynamics, i.e., different values of ?2. The extrapolated empirical dike-to-cone sheet transition is in good agreement with the occurrence of dikes and cone sheets in various natural volcanic settings.

Galland, Olivier; Burchardt, Steffi; Hallot, Erwan; Mourgues, Régis; Bulois, Cédric

2014-08-01

254

Displacement currents associated with the insertion of Alzheimer disease amyloid beta-peptide into planar bilayer membranes.  

PubMed Central

The role of endogenous amyloid beta-peptides as causal factors of neurodegenerative diseases is largely unknown. We have previously reported that interactions between Alzheimer's disease A beta P[1-40] peptide in solution and planar bilayer membranes made from anionic phospholipids lead to the formation of cation-selective channels. We now find and report here that the spontaneous insertion of free A beta P[1-40] across the bilayer can be detected as an increase in bilayer capacity. To this end we recorded the displacement currents across planar bilayers (50 mM KCl on both sides) in response to sudden displacements of the membrane potential, from -300 to 300 mV in 20-mV increments. To monitor the A beta P[1-40]-specific displacement currents, we added A beta P[1-40] (1-5 microM) to the solution on either side of the membrane and noted that the direction of the displacement current depended on the side with A beta P[1-40]. The size of the A beta P[1-40]-specific charge displaced during a pulse was always equal to the charge returning to the original configuration after the pulse, suggesting that the dipole molecules are confined to the membrane. As a rule, the steady-state distribution of the A beta P[1-40]-specific charges within the bilayer could be fit by a Boltzmann distribution. The potential at which the charges were found to be equally distributed (V(o)) were approximately -135 mV (peptide added to the solution in the compartment electrically connected to earth) and 135 mV (peptide added to the solution connected to the input of the amplifier). The A beta P[1-40]-specific transfer of charge reached a maximum value (Q(max)) when the electrical potential of the side containing the amyloid beta-protein was taken to either -300 or 300 mV. For a circular membrane of 25-microm radius ( approximately 2000 microm(2)), the total A beta P[1-40]-specific charge Q(max) was estimated as 55 fC, corresponding to some 170 e.c./microm(2). Regardless of the side selected for the addition of A beta P[1-40], at V(o) the charge displaced underwent an e-fold change for a approximately 27-mV change in potential. The effective valence (a) of the A beta P[1-40] dipole (i.e., the actual valence Z multiplied by the fraction of the electric field chi acting on the dipole) varied from 1 to 2 electronic charges. We also tested, with negative results, the amyloid peptide with the reverse sequence (A beta P[40-1]). These data demonstrate that A beta P[1-40] molecules can span the low dielectric domain of the bilayer, exposing charged residues (D(1), E(3), R(5), H(6), D(7), E(11), H(13), and H(14)) to the electric field. Thus the A beta P[1-40] molecules in solution must spontaneously acquire suitable conformations (beta-pleated sheet) allowing specific interactions with charged phospholipids. Interestingly, the domain from residues 676 to 704 in the APP(751) is homologous with the consensus sequence for lipid binding found in other membrane proteins regulated by anionic phospholipids. PMID:10920024

Vargas, J; Alarcon, J M; Rojas, E

2000-01-01

255

Ring current dynamics and plasma sheet sources. [magnetic storms  

NASA Technical Reports Server (NTRS)

The source of the energized plasma that forms in geomagnetic storm ring currents, and ring current decay are discussed. The dominant loss processes for ring current ions are identified as charge exchange and resonant interactions with ion-cyclotron waves. Ring current ions are not dominated by protons. At L4 and energies below a few tens of keV, O+ is the most abundant ion, He+ is second, and protons are third. The plasma sheet contributes directly or indirectly to the ring current particle population. An important source of plasma sheet ions is earthward streaming ions on the outer boundary of the plasma sheet. Ion interactions with the current across the geomagnetic tail can account for the formation of this boundary layer. Electron interactions with the current sheet are possibly an important source of plasma sheet electrons.

Lyons, L. R.

1984-01-01

256

Monoatomically thin polarizable sheets  

NASA Astrophysics Data System (ADS)

We consider a flat lattice of dipoles modeled by harmonic oscillators interacting with the electromagnetic field in the dipole approximation. Eliminating the variables from the coupled equations of motion, we come to effective Maxwell equations. These allow for taking the lattice spacing a to zero. As a result, we obtain reflection coefficients for the scattering of electromagnetic waves off the sheet. These are a generalization of that known from the hydrodynamic model. For instance, we get a nontrivial scattering for polarizability perpendicular to the sheet. Also, we show that the case of polarizability parallel to the sheet can be obtained in a natural way from a plasma layer of finite thickness. As an alternative approach, we discuss the elimination of the electromagnetic fields resulting in effective equations for the oscillators. These are shown, for a?0, divergent behavior, resulting from the electrostatic interaction of the dipoles.

Bordag, M.

2014-06-01

257

Sheet Music Consortium  

NSDL National Science Digital Library

For those who love everything from Sousa to show tunes, the Sheet Music Consortium is a fabulous find. The Consortium is comprised of a number of member libraries (including UCLA) who are interested in building "an open collection of digitized sheet music." Their work has been supported by the Institute of Museum and Library Services and currently offers cross collection searching of 22 sheet music collections, with a total of 226,000 items. Visitors can click on the Virtual Collection to get started with offerings such as "Texas Cowboy Songs" and "The Titanic." The Browse feature is a great way to get a sense of the materials here. Finally, the Activity Stream provides an updated list of the most recently added items for general consumption. [KMG

2013-02-15

258

California Sheet Music Project  

NSDL National Science Digital Library

With oversight provided by Professor Mary Kay Duggan of the University of California at Berkeley, the California Sheet Music Project provides online access to some 2000 pieces of sheet music published in California between 1852 and 1900. The project was funded by the U.S. Institute of Museum and Library Services, and also contains interesting ephemera ranging from a music publisher's catalog from 1872, advertisements, and photographs. The entire database may be searched or browsed by image subject (from the frontispiece of each composition) or by the subject addressed by each piece of music. Some of the songs included in the archive deal with beggars ("Just One Penny to Buy Bread," babies ("Baby's Asleep"), and politicians ("Horace Greeley's Grand March"). Finally the site also has several musical performances of pieces from the collection for the listening pleasure of those compelled to visit this interesting tribute to the sheet music of the Golden State.

Duggan, Mary K.

259

Historic American Sheet Music  

NSDL National Science Digital Library

Duke University's Historic American Sheet Music Project (HASM) presents digital images of 3,042 pieces of sheet music from Duke's collections, published between 1850 and 1920. Highlights of the collection include "antebellum Southern music, Confederate imprints, and Civil war songs." The search capabilities at the site are sophisticated, allowing users to look for music by publisher name, composer, title, performer, and many other terms. There is online help for searching and a glossary of subject headings. Much of the sheet music is illustrated, and it is possible to search for pictures by "illustration type" (theme), allowing access to the subjects of the illustrations as well as the music itself. It is also possible to browse all the cover illustrations. HASM was originally funded by Ameritech as part of the ongoing Library of Congress/Ameritech Digital Library Competition; it will soon be part of the American Memory Collections at the Library of Congress (described in the November 6, 1998 Scout Report).

1999-01-01

260

Historic Sheet Music  

NSDL National Science Digital Library

If you're looking for compelling sheet music from decades gone by, this website from the University of Oregon Libraries is just the ticket. Initially created to showcase sheet music from the Oregon Music Collection, their digitization work continues apace, and there are already over 650 pieces of sheet music available here. Visitors to the site can browse the collection by title, composer, or topic. Perhaps the most unique items here are those pieces composed by Oregonian women, such as Amy Beach, Marion Bauer, and Liza Lehmann. Not surprisingly, the collection is also strong in the area of Western Americana, as attested to by songs like "Broncho Buster", "Oh you round up, let 'er buck", and "The Gray Haired Pioneer".

261

Roles of the {beta} subunit hinge domain in ATP synthase F{sub 1} sector: Hydrophobic network formed by introduced {beta}Phe174 inhibits subunit rotation  

SciTech Connect

The ATP synthase {beta} subunit hinge domain ({beta}Phe148 {approx} {beta}Gly186, P-loop/{alpha}-helixB/loop/{beta}-sheet4, Escherichia coli residue numbering) dramatically changes in conformation upon nucleotide binding. We previously reported that F{sub 1} with the {beta}Ser174 to Phe mutation in the domain lowered the {gamma} subunit rotation speed, and thus decreased the ATPase activity [M. Nakanishi-Matsui, S. Kashiwagi, T. Ubukata, A. Iwamoto-Kihara, Y. Wada, M. Futai, Rotational catalysis of Escherichia coli ATP synthase F{sub 1} sector. Stochastic fluctuation and a key domain of the {beta} subunit, J. Biol. Chem. 282 (2007) 20698-20704.]. Homology modeling indicates that the amino acid replacement induces a hydrophobic network, in which the {beta}Met159, {beta}Ile163, and {beta}Ala167 residues of the {beta} subunit are involved together with the mutant {beta}Phe174. The network is expected to stabilize the conformation of {beta}{sub DP} (nucleotide-bound form of the {beta} subunit), resulting in increased activation energy for transition to {beta}{sub E} (empty {beta} subunit). The modeling further predicts that replacement of {beta}Met159 with Ala or Ile weakens the hydrophobic network. As expected, these two mutations experimentally suppressed the ATPase activities as well as subunit rotation of {beta}S174F. Furthermore, the rotation rate decreased with the increase of the strength in the hydrophobic network. These results indicate that the smooth conformational change of the {beta} subunit hinge domain is pertinent for the rotational catalysis.

Nakanishi-Matsui, Mayumi; Kashiwagi, Sachiko [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694 (Japan)] [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694 (Japan); Kojima, Masaki [Tokyo University of Pharmacy and Life Sciences, Hachiohji, Tokyo 192-0392 (Japan)] [Tokyo University of Pharmacy and Life Sciences, Hachiohji, Tokyo 192-0392 (Japan); Nonaka, Takamasa [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694 (Japan)] [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694 (Japan); Futai, Masamitsu, E-mail: futaim@iwate-med.ac.jp [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694 (Japan)] [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694 (Japan)

2010-04-30

262

The ice sheet model The polythermal ice sheet  

E-print Network

. The simulated HEs affect large areas of the Laurentide ice sheet. Up to 15 percentage of ice volume can (Fig- ure 4f). The Laurentide ice sheet changes between a single-dome and a multi- dome complex during

Calov, Reinhard

263

71. PALMDALE WATER COMPANY, EASTWOOD MULTIPLEARCHED DAM: STRESS SHEET, SHEET ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

71. PALMDALE WATER COMPANY, EASTWOOD MULTIPLE-ARCHED DAM: STRESS SHEET, SHEET 3; DECEMBER 20, 1918. Littlerock Water District files. - Little Rock Creek Dam, Little Rock Creek, Littlerock, Los Angeles County, CA

264

Kepler Mission Fact Sheet  

NSDL National Science Digital Library

This 2-page color fact sheet briefly describes NASA's Kepler mission, its instruments, and ground system. Also included are tables listing the instrument parameters and the major institutions involved. Kepler is a spaceborne telescope specifically designed to survey our region of the Milky Way galaxy to detect and characterize hundreds of Earth-size and smaller planets in or near the habitable zone. The habitable zone encompasses the distances from a star where liquid water can exist on a planet's surface. Note: The fact sheets states that the Kepler Telescope was launched in 2007 but did not launch until 2009.

265

Curved cap corrugated sheet  

NASA Technical Reports Server (NTRS)

The report describes a structure for a strong, lightweight corrugated sheet. The sheet is planar or curved and includes a plurality of corrugation segments, each segment being comprised of a generally U-shaped corrugation with a part-cylindrical crown and cap strip, and straight side walls and with secondary corrugations oriented at right angles to said side walls. The cap strip is bonded to the crown and the longitudinal edge of said cap strip extends beyond edge at the intersection between said crown and said side walls. The high strength relative to weight of the structure makes it desirable for use in aircraft or spacecraft.

Davis, R. C.; Bales, T. T.; Royster, D. M.; Jackson, L. R. (inventors)

1984-01-01

266

Low-Temperature Forming of Beta Titanium Alloys  

NASA Technical Reports Server (NTRS)

Low cost methods for titanium structural fabrication using advanced cold-formable beta alloys were investigated for application in a Mach 2.7 supersonic cruise vehicle. This work focuses on improving processing and structural efficiencies as compared with standard hot formed and riveted construction of alpha-beta alloy sheet structure. Mechanical property data and manufacturing parameters were developed for cold forming, brazing, welding, and processing Ti-15V-3Cr-3Sn-3Al sheet, and Ti-3Al-8V-6Cr-4Zr on a more limited basis. Cost and structural benefits were assessed through the fabrication and evaluation of large structural panels. The feasibility of increasing structural efficiency of beta titanium structure by selective reinforcement with metal matrix composite was also explored.

Kaneko, R. S.; Woods, C. A.

1983-01-01

267

Core binding factor beta (Cbf?) controls the balance of chondrocyte proliferation and differentiation by upregulating Indian hedgehog (Ihh) expression and inhibiting parathyroid hormone-related protein receptor (PPR) expression in postnatal cartilage and bone formation.  

PubMed

Core binding factor beta (Cbf?) is essential for embryonic bone morphogenesis. Yet the mechanisms by which Cbf? regulates chondrocyte proliferation and differentiation as well as postnatal cartilage and bone formation remain unclear. Hence, using paired-related homeobox transcription factor 1-Cre (Prx1-Cre) mice, mesenchymal stem cell-specific Cbf?-deficient (Cbf?(f/f) Prx1-Cre) mice were generated to study the role of Cbf? in postnatal cartilage and bone development. These mutant mice survived to adulthood but exhibited severe sternum and limb malformations. Sternum ossification was largely delayed in the Cbf?(f/f) Prx1-Cre mice and the xiphoid process was noncalcified and enlarged. In newborn and 7-day-old Cbf?(f/f) Prx1-Cre mice, the resting zone was dramatically elongated, the proliferation zone and hypertrophic zone of the growth plates were drastically shortened and disorganized, and trabecular bone formation was reduced. Moreover, in 1-month-old Cbf?(f/f) Prx1-Cre mice, the growth plates were severely deformed and trabecular bone was almost absent. In addition, Cbf? deficiency impaired intramembranous bone formation both in vivo and in vitro. Interestingly, although the expression of Indian hedgehog (Ihh) was largely reduced, the expression of parathyroid hormone-related protein (PTHrP) receptor (PPR) was dramatically increased in the Cbf?(f/f) Prx1-Cre growth plate, indicating that that Cbf? deficiency disrupted the Ihh-PTHrP negative regulatory loop. Chromatin immunoprecipitation (ChIP) analysis and promoter luciferase assay demonstrated that the Runx/Cbf? complex binds putative Runx-binding sites of the Ihh promoter regions, and also the Runx/Cbf? complex directly upregulates Ihh expression at the transcriptional level. Consistently, the expressions of Ihh target genes, including CyclinD1, Ptc, and Pthlh, were downregulated in Cbf?-deficient chondrocytes. Taken together, our study reveals not only that Cbf? is essential for chondrocyte proliferation and differentiation for the growth and maintenance of the skeleton in postnatal mice, but also that it functions in upregulating Ihh expression to promoter chondrocyte proliferation and osteoblast differentiation, and inhibiting PPR expression to enhance chondrocyte differentiation. PMID:24821091

Tian, Fei; Wu, Mengrui; Deng, Lianfu; Zhu, Guochun; Ma, Junqing; Gao, Bo; Wang, Lin; Li, Yi-Ping; Chen, Wei

2014-07-01

268

Asymmetric Magnetic Reconnection in Coronal Mass Ejection Current Sheets  

NASA Astrophysics Data System (ADS)

Flux rope models of coronal mass ejections (CMEs) predict the formation of an elongated current sheet in the wake behind the rising plasmoid. Magnetic reconnection in these current sheets is highly asymmetric. Sunward outflow impacts the post-flare loops and regions of high plasma and magnetic pressure, whereas antisunward outflow impacts the rising flux rope. There are strong gradients along the outflow direction for upstream density, pressure, and magnetic field strength. Resistive magnetohydrodynamic simulations of X-line retreat predict that the majority of the outflow energy is directed upward because the principal X-line is located near the lower base of the current sheet. We derive an exact expression showing that the rate of X-line retreat is given by a combination of advection and diffusion. During line-tied reconnection with asymmetric upstream magnetic field strengths, the structure of the post-flare loops is skewed and the current sheet drifts along the inflow direction. We compare the drift rate to observations of CME current sheets that characteristically drift or tilt with time, including the 2008 April 9 "Cartwheel CME." We will present simulations of plasmoid formation in high Lundquist number current sheets, and report our progress using time-dependent ionization to predict observational signatures from simulations of CME current sheets.

Murphy, N. A.; Miralles, M. P.; Pope, C. L.; Raymond, J. C.; Young, A. K.; Shen, C.; Lin, J.; Reeves, K. K.; Seaton, D. B.; Webb, D. F.

2011-12-01

269

Raman and AFM study of gamma irradiated plastic bottle sheets  

SciTech Connect

In this investigation, the effects of gamma irradiation on the structural properties of plastic bottle sheet are studied. The Plastic sheets were exposed with 1.25MeV {sup 60}Co gamma rays source at various dose levels within the range from 0-670 kGy. The induced modifications were followed by micro-Raman and atomic force microscopy (AFM). The Raman spectrum shows the decrease in Raman intensity and formation of unsaturated bonds with an increase in the gamma dose. AFM image displays rough surface morphology after irradiation. The detailed Raman analysis of plastic bottle sheets is presented here, and the results are correlated with the AFM observations.

Ali, Yasir; Kumar, Vijay; Dhaliwal, A. S. [Department of Physics, Sant Longowal Institute of Engineering and Technology Longowal, Punjab-148106 (India); Sonkawade, R. G. [School of Physical Sciences, Babasaheb Bhimrao Ambedkar University, Lucknow-226025 (India)

2013-02-05

270

Raman and AFM study of gamma irradiated plastic bottle sheets  

NASA Astrophysics Data System (ADS)

In this investigation, the effects of gamma irradiation on the structural properties of plastic bottle sheet are studied. The Plastic sheets were exposed with 1.25MeV 60Co gamma rays source at various dose levels within the range from 0-670 kGy. The induced modifications were followed by micro-Raman and atomic force microscopy (AFM). The Raman spectrum shows the decrease in Raman intensity and formation of unsaturated bonds with an increase in the gamma dose. AFM image displays rough surface morphology after irradiation. The detailed Raman analysis of plastic bottle sheets is presented here, and the results are correlated with the AFM observations.

Ali, Yasir; Kumar, Vijay; Sonkawade, R. G.; Dhaliwal, A. S.

2013-02-01

271

Student Data Sheet Crystal Experiment: _______________________________  

E-print Network

Student Data Sheet Name: Date: Crystal Experiment: _______________________________ Observations: Day One Day Two Crystal Experiment: ______________________________ Observations: Day One Day Two #12;Student Data Sheet Name: Date: Observations of Crystals Name of Crystal Observation Bismuth Pyrite

Pike, Robert D.

272

Radiation Therapy Side Effects Sheets  

Cancer.gov

Radiation therapy fact sheets that help patients understand their treatment and manage side effects. The fact sheets (also available in audio) have tips from patients and healthcare providers, and questions to ask providers.

273

Cascading Style Sheets  

NSDL National Science Digital Library

Cascading style sheets allow for greater control over how a web document is presented, and this site can help interested users learn about them. W3C's CSS page offers even more information regarding CSS, it's history, and what's new. It also provides a listing of other related guides and tools.

1997-01-01

274

Software Fact Sheet Description  

E-print Network

Software Fact Sheet Description Display & Analysis Software Data Access Software www.unidata.ucar.edu/software, and multidisciplinary integration, Unidata provides a rich set of software tools to access and visualize Earth with the aid of three tools: the LDM, RAMADDA and the TDS. Data Management Software Unidata facilitates

275

Participant Guide Cover Sheet  

E-print Network

Proposal Management Reviewer Participant Guide Cover Sheet Last updated: 03/20/09 1 of 1 http Page 1 #12;Proposal Management Reviewer Participant Guide Last updated: 03/09/09 1 of 1 http Management - State Transitions Page 4 #12;Proposal Management Reviewer Participant Guide Last updated: 03

Shyy, Wei

276

Gamma, Beta, Erf  

NSDL National Science Digital Library

This page includes the encyclopedia entries for gamma, beta and erf functions including factorials, binomials, gamma functions and inverses, differentiated gamma functions, beta functions and inverses, probability integrals and inverses, Frensnel integrals and exponential integrals.

277

Slow Mode Waves in the Heliospheric Plasma Sheet  

NASA Technical Reports Server (NTRS)

We report the results of a search for waves/turbulence in the Heliospheric Plasma Sheet (HPS) surrounding the Heliospheric Current Sheet (HCS). The HPS is treated as a distinctive heliospheric structure distinguished by relatively high Beta, slow speed plasma. The data used in the investigation are from a previously published study of the thicknesses of the HPS and HCS that were obtained in January to May 2004 when Ulysses was near aphelion at 5 AU. The advantage of using these data is that the HPS is thicker at large radial distances and the spacecraft spends longer intervals inside the plasma sheet. From the study of the magnetic field and solar wind velocity components, we conclude that, if Alfven waves are present, they are weak and are dominated by variations in the field magnitude, B, and solar wind density, NP, that are anti-correlated.

Smith, Edward. J.; Zhou, Xiaoyan

2007-01-01

278

Detection of localized, plasma-depleted flux tubes or bubbles in the midtail plasma sheet  

Microsoft Academic Search

Recent studies have shown that most Earthward transport in the midtail, high-beta plasma sheet takes place in the form of short-lived, high-speed plasma flow bursts. Bursty bulk flows are observed both when the plasma sheet ishin, such as during substorm expansion, and when it is thick, such as during substorm recovery. We present multi-instrument observations from the ISEE 1 and

V. A. Sergeev; V. Angelopoulos; J. T. Gosling; C. A. Cattell; C. T. Russell

1996-01-01

279

The Physics of Ice Sheets  

ERIC Educational Resources Information Center

The great ice sheets in Antarctica and Greenland are vast deposits of frozen freshwater that contain enough to raise sea level by approximately 70 m if they were to completely melt. Because of the potentially catastrophic impact that ice sheets can have, it is important that we understand how ice sheets have responded to past climate changes and…

Bassis, J. N.

2008-01-01

280

Cross-talk between integrins {alpha}1{beta}1 and {alpha}2{beta}1 in renal epithelial cells  

SciTech Connect

The collagen-binding integrins {alpha}1{beta}1 and {alpha}2{beta}1 have profoundly different functions, yet they are often co-expressed in epithelial cells. When both integrins are expressed in the same cell, it has been suggested that {alpha}1{beta}1 negatively regulates integrin {alpha}2{beta}1-dependent functions. In this study we utilized murine ureteric bud (UB) epithelial cells, which express no functionally detectable levels of endogenous integrins {alpha}1{beta}1 and {alpha}2{beta}1, to determine the mechanism whereby this regulation occurs. We demonstrate that UB cells expressing integrin {alpha}2{beta}1, but not {alpha}1{beta}1 adhere, migrate and proliferate on collagen I as well as form cellular cords in 3D collagen I gels. Substitution of the transmembrane domain of the integrin {alpha}2 subunit with that of {alpha}1 results in decreased cell adhesion, migration and cord formation. In contrast, substitution of the integrin {alpha}2 cytoplasmic tail with that of {alpha}1, decreases cell migration and cord formation, but increases proliferation. When integrin {alpha}1 and {alpha}2 subunits are co-expressed in UB cells, the {alpha}1 subunit negatively regulates integrin {alpha}2{beta}1-dependent cord formation, adhesion and migration and this inhibition requires expression of both {alpha}1 and {alpha}2 tails. Thus, we provide evidence that the transmembrane and cytoplasmic domains of the {alpha}2 integrin subunit, as well as the {alpha}1 integrin subunit, regulate integrin {alpha}2{beta}1 cell function.

Abair, Tristin D. [Department of Medicine, Division of Nephrology, Vanderbilt University, Nashville, TN 37232 (United States); Department of Cancer Biology, Vanderbilt University, Nashville, TN 37232 (United States); Sundaramoorthy, Munirathinam; Chen, Dong [Department of Medicine, Division of Nephrology, Vanderbilt University, Nashville, TN 37232 (United States); Heino, Jyrki [Department of Biochemistry and Food Chemistry, University of Turku, Turku (Finland); Ivaska, Johanna [VTT Technical Research Centre of Finland, Medical Biotechnology, Turku (Finland); Hudson, Billy G. [Department of Medicine, Division of Nephrology, Vanderbilt University, Nashville, TN 37232 (United States); Department of Biochemistry, Vanderbilt University, Nashville, TN 37232 (United States); Sanders, Charles R. [Department of Biochemistry, Vanderbilt University, Nashville, TN 37232 (United States); Pozzi, Ambra [Department of Medicine, Veterans Affairs Hospital, Nashville, TN 37232 (United States); Department of Medicine, Division of Nephrology, Vanderbilt University, Nashville, TN 37232 (United States); Department of Cancer Biology, Vanderbilt University, Nashville, TN 37232 (United States); Zent, Roy [Department of Medicine, Veterans Affairs Hospital, Nashville, TN 37232 (United States); Department of Medicine, Division of Nephrology, Vanderbilt University, Nashville, TN 37232 (United States); Department of Cancer Biology, Vanderbilt University, Nashville, TN 37232 (United States); Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232 (United States)], E-mail: roy.zent@vanderbilt.edu

2008-11-15

281

Sheet Music from Canada's Past  

NSDL National Science Digital Library

The National Library of Canada has recently updated their collection of historical Canadian sheet music. Sheet Music from Canada's Past (see the November 17, 2000 Scout Report for an earlier mention) has updated their collection of sheet music from the World War I era with sheet music published before the Confederation in 1867. One can search the entire collection or search the World War I and pre-Confederation collections separately. The site also features articles devoted to describing each collection, and the posted music may be printed out from the site. Future plans include digitizing sheet music published between 1867 and 1913.

2001-01-01

282

Graphene oxide strongly inhibits amyloid beta fibrillation  

NASA Astrophysics Data System (ADS)

Since amyloid beta fibrillation (A?F) plays an important role in the development of neurodegenerative diseases, we investigated the effect of graphene oxide (GO) and their protein-coated surfaces on the kinetics of A? fibrillation in the aqueous solution. We showed that GO and their protein-covered surfaces delay the A?F process via adsorption of amyloid monomers. Also, the large available surface of GO sheets can delay the A?F process by adsorption of amyloid monomers. The inhibitory effect of the GO sheet was increased when we increase the concentration from 10% (in vitro; stimulated media) to 100% (in vivo; stimulated media). Conclusion: our results revealed that GO and their surface proteins inhibit A?F by decreasing the kinetic reaction.Since amyloid beta fibrillation (A?F) plays an important role in the development of neurodegenerative diseases, we investigated the effect of graphene oxide (GO) and their protein-coated surfaces on the kinetics of A? fibrillation in the aqueous solution. We showed that GO and their protein-covered surfaces delay the A?F process via adsorption of amyloid monomers. Also, the large available surface of GO sheets can delay the A?F process by adsorption of amyloid monomers. The inhibitory effect of the GO sheet was increased when we increase the concentration from 10% (in vitro; stimulated media) to 100% (in vivo; stimulated media). Conclusion: our results revealed that GO and their surface proteins inhibit A?F by decreasing the kinetic reaction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr31657a

Mahmoudi, Morteza; Akhavan, Omid; Ghavami, Mahdi; Rezaee, Farhad; Ghiasi, Seyyed Mohammad Amin

2012-11-01

283

Light Sheet Fluorescence Microscopy  

PubMed Central

Light sheet fluorescence microscopy (LSFM) functions as a non-destructive microtome and microscope that uses a plane of light to optically section and view tissues with subcellular resolution. This method is well suited for imaging deep within transparent tissues or within whole organisms, and because tissues are exposed to only a thin plane of light, specimen photobleaching and phototoxicity are minimized compared to wide-field fluorescence, confocal, or multiphoton microscopy. LSFMs produce well-registered serial sections that are suitable for three-dimensional reconstruction of tissue structures. Because of a lack of a commercial LSFM microscope, numerous versions of light sheet microscopes have been constructed by different investigators. This review describes development of the technology, reviews existing devices, provides details of one LSFM device, and shows examples of images and three-dimensional reconstructions of tissues that were produced by LSFM. PMID:21339178

Santi, Peter A.

2011-01-01

284

Irish Sheet Music Archives  

NSDL National Science Digital Library

Based out of Milwaukee, the Ward Irish Music Archives were established in 1992 and is dedicated to the preservation of Irish and Irish-American music in all of its forms. Visitors to this remarkable site can browse over 5,000 pieces of Irish and Irish-American sheet music. While some of these ditties are not in the public domain, the collection can be narrowed down by filtering for only publicly available items. The History section contains a topical history of sheet music from the days of the broadside to the more challenging days of the early 21st century when digital versions became dominant. The Galleries are another great feature, containing additional information about cover artists, composers, and themes. It's an amazing collection and one that will inspire a few sing-a-longs from Dublin to Boston.

285

Yiddish Sheet Music  

NSDL National Science Digital Library

The Brown University Library Center for Digital Initiatives has crafted well over a dozen excellent collections for use by the general public. This fine addition brings together Yiddish language sheet music from the John Hay Library. Most of the materials here came from the collection of Menache Vaxer, a Yiddish writer. The collection was acquired by the library in 1968, and it included over 850 pieces of piano-vocal or instrumental music, dating from the 1890s to the 1940s. Visitors can browse 327 pieces of sheet music by creator or title, and they will have access to the complete scores. There are some fascinating numbers here, including "Mameniu: Or the Triangle Victims" and "Beware of the Devil's Power."

286

Clean Cities Fact Sheet  

SciTech Connect

This fact sheet explains the Clean Cities Program and provides contact information for all coalitions and regional offices. It answers key questions such as: What is the Clean Cities Program? What are alternative fuels? How does the Clean Cities Program work? What sort of assistance does Clean Cities offer? What has Clean Cities accomplished? What is Clean Cities International? and Where can I find more information?

Not Available

2004-01-01

287

Vanishing Polar Ice Sheets  

Microsoft Academic Search

\\u000a Global temperatures have increased by 0.8°C since instrumental records began, and the last decade has been the warmest. This\\u000a warming has been closely linked to increasing greenhouse gas concentrations due to human activities. Arctic warming is leading\\u000a to thinning and disappearance of sea ice on the Arctic Ocean and the increased melting of the Greenland ice sheet. In the\\u000a last

Nancy A. N. Bertler; Peter J. Barrett

288

Quarter-sheet questions  

NASA Astrophysics Data System (ADS)

The first day or two can set the stage for a positive relationship between the teacher and the students. "Icebreakers" are often used to start the conversation. Here I describe the use of quarter-sheet questions to not only get my students talking early on, but also to have them realize that I am willing to look into peripheral areas of interest to them as well as make clear what my objectives are for them.

Hubisz, John L.

2010-02-01

289

Honda Civic fact sheet  

SciTech Connect

The U.S. Department of Energy (DOE) is promoting the use of alternative fuels and alternative fuel vehicles (AFVs). The National Renewable Energy Laboratory (NREL) has been directed to conduct projects to evaluate the performance and acceptability of light-duty AFVs. This fact sheet describes the test results on 1998 Honda Civics: one dedicated CNG and a gasoline model as closely matched as possible.

NREL

1999-05-01

290

Kepler Mission Fact Sheet  

NSDL National Science Digital Library

This 2-page color fact sheet briefly describes NASAâs Kepler mission, its instruments, and ground system. Also included are tables listing the instrument parameters and the major institutions involved. Kepler is a spaceborne telescope specifically designed to survey our region of the Milky Way galaxy to detect and characterize hundreds of Earth-size and smaller planets in or near the habitable zone. The habitable zone encompasses the distances from a star where liquid water can exist on a planet's surface.

2007-01-01

291

Between the Sheets: Accounting  

NSDL National Science Digital Library

This guide from the British Website BizEd helps users understand the ways to use spreadsheets in accounting. The tutorial starts with general information: introductions for both students and teachers, a guide to downloadable spreadsheets, a guide to using spreadsheets, and a glossary of important terms. The guide offers a collection of spreadsheets that require Microsoft Excel 97. Also featured is an introduction to balance sheets and income statements, budgeting, and cost volume profit analysis.

2007-05-14

292

Differences in cytotoxicity of ?-sheet peptides originated from silk and amyloid ?.  

PubMed

The relationships between amino acid sequence, nano-assemblies, and cytotoxicity to neuron cytotoxicity were investigated using ?-sheet-forming peptides from Araneus ventricosus spider silk, and amyloid forming peptides A?(12-28) (?1), A?(28-42) (?2), and full-length A?(1-42). Although silk derived peptides formed nano-assemblies, nanofilaments, and nanofibrils with ?-sheet contents raging from 24 to 40%, they showed no significant cytotoxicity to neurons. In contrast, nano-assemblies and nanofibrils formed from A? peptides with high ?-sheet content demonstrated cytotoxicity to the neurons. These differences in cell response between the silk ?-sheets and A? peptides indicate that the general propensity to form beta sheets and form nanostructures is not sufficient to predict cytotoxicity, while surface charges of the assemblies are significant factors that impact cytotoxicity. PMID:20954203

Numata, Keiji; Kaplan, David L

2011-01-10

293

DEVELOPMENT OF A BETA 0.12, 88 MHZ, QUARTER WAVE RESONATOR AND ITS CRYOMODULE FOR THE SPIRAL2 PROJECT  

E-print Network

: Beta 0.12 QWR during the fabrication RRR250 Niobium sheets from TokyoDenkaï were used: 4-mm thick for the cavity walls and 3-mm thick for the stem. The beam tubes and ports aperture is 36 mm. Figure 2: Beta 0

Paris-Sud XI, Université de

294

Cellulose wet wiper sheets prepared with cationic polymer and carboxymethyl cellulose using a papermaking technique  

Microsoft Academic Search

Carboxymethyl cellulose (CMC)-rich cellulose sheets were prepared with a cationic retention aid, poly[N,N,N-trimethyl-N-(2-methacryloxyethyl)ammonium chloride] (PTMMAC), using a papermaking technique. When 5% PTMMAC and 5% CMC were added to\\u000a cellulose slurries, approximately 94% of the polymers were retained in the sheets by formation of polyion complexes between\\u000a the two polymers. When the PTMMAC\\/CMC\\/cellulose sheets were soaked in solutions consisting of ethanol,

Takehiko Uematsu; Yoshiaki Matsui; Shusuke Kakiuchi; Akira Isogai

2011-01-01

295

Asymmetric Magnetic Reconnection in Coronal Mass Ejection Current Sheets  

NASA Astrophysics Data System (ADS)

Flux rope models of coronal mass ejections (CMEs) predict the formation ofan elongated current sheet in the wake behind the rising plasmoid. These current sheets have been seen to drift or tilt over time by instruments including SOHO/LASCO and Hinode/XRT. We measure this in multiple observations including the 2008 April 9 "Cartwheel CME" and find an average drift that is far more than can be accounted for via the effects of solar rotation. The observed drift could be due to different parts of the current sheet actively reconnecting at different times (e.g., Savage et al. 2010), macroscopic effects from the rising flux rope pulling the plasma sheet along with it, or asymmetry in the magnetic reconnection process itself. These drift rates are compared with resistive magnetohydrodynamic (MHD) simulations of line-tied reconnection between magnetic fields of different strengths. The observed drift rates are comparable to predictions made by the simulations.

Pope, Crystal; Miralles, M. P.; Murphy, N. A.

2012-01-01

296

Magnetoacoustic waves in diagnostics of the flare current sheets  

NASA Astrophysics Data System (ADS)

Aims: To obtain diagnostics tools for solar flare current sheets, we numerically studied impulsively generated magnetoacoustic waves in the Harris current sheet. Methods: We used two-dimensional (2-D) magnetohydrodynamic (MHD) and wave dispersion models. Tests of these models were performed for waves in the density slab, where analytical solutions are known. In the MHD model, we solved the full set of ideal MHD equations by means of the modified two-step Lax-Wendroff algorithm. The initial perturbation was chosen to generate preferentially the fast sausage magnetoacoustic waves. To determine the dispersion characteristics of MHD waves in the Harris current sheet, we numerically solved the equation of plasma motions by means of the Runge-Kutta fourth order method together with the bisection iteration one. To establish some diagnostics of these waves and their corresponding flare current sheets, we used the wavelet analysis method. Results: We find that the results of tests of our 2-D MHD and wave dispersion models for the density slab are in good agreement with analytical results. We analyze the magnetoacoustic waves in the current sheet and compare them with those in the density slab. In both cases, for similar geometrical and plasma parameters, we find that wave trains were generated and propagated in a similar way. Their signals registered at selected locations of the Harris current sheet and density slab are also similar. Nevertheless, a dependence of the period of the magnetoacoustic waves on the width of the Harris current sheet differs from that for the density slab. The form of the wave front inside the current sheet similarly differs from that in the density slab. We find that the wavelet spectra of the signals of incoming magnetoacoustic waves at selected locations in the current sheet have the form of wavelet tadpoles. We distinguish that the form of these wavelet tadpoles becomes longer and the heads of the wavelet tadpoles are detected later in time as the distance of the detection point from that of the initial wave perturbation increases. We also find that the wavelet tadpole period depends on the plasma beta parameter. The results are discussed from the point of view of their use as diagnostics of the flare current sheets or flare loops.

Jelínek, P.; Karlický, M.

2012-01-01

297

Planetary Fact Sheets  

NSDL National Science Digital Library

Offered by the National Space Science Data Center of NASA, the Planetary Fact Sheets Web site contains helpful information for students studying astronomy. The site lists links to all of the planets, their satellites, and their rings, as well as to tables comparing all the planets. The planet pages contain a photograph and a simple list of dozens of facts such as mass, volume, distance to the earth, temperature, and much more. Although not flashy, the information provided by this site can be very useful to anyone wanting to learn more about our solar system.

1969-12-31

298

Balance-sheet trends  

E-print Network

operationss the legal capital at the end of the accasnt ing period~ followed by a subdivision of legal capital into the amount that is working capital and deferred cost to future operati"ns+ paten makes the following coueent concerning the above statements... compared to studies made try others a i'ew years ssrli. er, clearly india~tee the increasing use of ths eeaparative st~teaent? Cnly when uniform statements for a period of years are coogw'red can any paten, "Balance Sheet", Conte ors Account , Chapter 0...

Cox, Gilford W

2012-06-07

299

Fact Sheets from the ERIC Clearinghouse on Handicapped and Gifted Children: 1978 Series.  

ERIC Educational Resources Information Center

A series of six fact sheets giving basic information on specific subjects of interest to those working with handicapped and gifted children. The fact sheets, developed by the ERIC (Educational Resources Information Center) Clearinghouse on Handicapped and Gifted Children during fiscal year 1978, are designed in a question/answer format and have…

Council for Exceptional Children, Reston, VA. Information Center on Exceptional Children.

300

PROGRAMMING AND DISCRETE MATHEMATICS (XX10190) SEMESTER 2 MATHEMATICS: PROBLEM SHEET 5  

E-print Network

one at http://people.bath.ac.uk/masgks/Discrete/sheet5.pdf in PDF, and in other formats nearby. All the large numbers in this sheet are assigned to MatLab variables in the MatLab script GKS5nums 20 + 1243. Alice wishes to send Bob the secret message m, which is actually 10 20 (and therefore

Sankaran, Gregory R.

301

PROGRAMMING AND DISCRETE MATHEMATICS (XX10190) SEMESTER 2 MATHEMATICS: PROBLEM SHEET 4  

E-print Network

one at http://people.bath.ac.uk/masgks/Discrete/sheet4.pdf in PDF, and in other formats nearby. All the large numbers in this sheet are assigned to MatLab variables in the MatLab script GKS4nums a message m, which is also an element of F q , she simply computes am. Of course Bob cannot decrypt this

Sankaran, Gregory R.

302

PROGRAMMING AND DISCRETE MATHEMATICS (XX10190) SEMESTER 2 MATHEMATICS: PROBLEM SHEET 5  

E-print Network

one at http://people.bath.ac.uk/masgks/Discrete/sheet5.pdf in PDF, and in other formats nearby. All the large numbers in this sheet are assigned to MatLab variables in the MatLab script GKS5nums. Alice wishes to send Bob the secret message m, which is actually 1020 (and therefore a square

Sankaran, Gregory R.

303

PROGRAMMING AND DISCRETE MATHEMATICS (XX10190) SEMESTER 2 MATHEMATICS: PROBLEM SHEET 4  

E-print Network

one at http://people.bath.ac.uk/masgks/Discrete/sheet4.pdf in PDF, and in other formats nearby. All the large numbers in this sheet are assigned to MatLab variables in the MatLab script GKS4nums a message m, which is also an element of Fq, she simply computes am. Of course Bob cannot decrypt this

Sankaran, Gregory R.

304

[Clip Sheets from BOCES. Opportunities. Health. Careers. = Oportunidades. Salud. Una Camera En...  

ERIC Educational Resources Information Center

This collection of 83 clip sheets, or classroom handouts, was created to help U.S. migrants learn more about health, careers, and general "opportunities" including education programs. They are written in both English and Spanish and are presented in an easily understandable format. Health clip-sheet topics include the following: Abuse; AIDS;…

State Univ. of New York, Geneseo. Coll. at Geneseo. Migrant Center.

305

Numerical modeling investigations of the subglacial conditions of the southern Laurentide ice sheet  

Microsoft Academic Search

Sub- and proglacial bed conditions influence advance and retreat of an ice sheet. The existence and distribution of frozen ground is of major importance for better understanding of ice-flow dynamics and landform formation. The southern margin of the Laurentide ice sheet (LIS) was dominated by the presence of relatively thin ice lobes that seem to have been very sensitive to

Andreas Bauder; David M. Mickelson; Shawn J. Marshall

2005-01-01

306

Method for heating a glass sheet  

DOEpatents

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed. 5 figs.

Boaz, P.T.

1998-07-21

307

Method for heating a glass sheet  

DOEpatents

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed.

Boaz, Premakaran Tucker (Livonia, MI)

1998-01-01

308

Effect of beta-cyclodextrin and hydroxypropyl beta-cyclodextrin complexation on physicochemical properties and antimicrobial activity of cefdinir.  

PubMed

The solid-state properties, dissolution profile and antimicrobial activity of inclusion complexes of cefdinir (CEF) with beta-cyclodextrin (betaCD) and hydroxypropyl beta-cyclodextrin (HPbetaCD) were investigated. The phase solubility profiles of cefdinir with betaCD and HPbetaCD were classified as A(L)-type, which indicates the formation of 1:1 stoichiometry inclusion complexes. Stability constants with 1:1 molar ratio obtained from the phase solubility diagrams were 120.38+/-1.07 and 58.60+/-1.20 M(-1) for betaCD and HPbetaCD, respectively. Binary systems of CEF with betaCD and HPbetaCD prepared by kneading method were characterized by Fourier transformation-infrared spectroscopy (FTIR) and X-ray powder diffractometry (XRD). The aqueous solubility of CEF was enhanced by 101% for betaCD and 23.4% for HPbetaCD, respectively. The dissolution profiles of inclusion complexes were determined and compared with those of CEF alone and their physical mixtures. The dissolution rate of CEF was increased by betaCD and HPbetaCD inclusion complexation moderately. However, the antimicrobial activity of CEF was increased significantly (p<0.001) by betaCD and HPbetaCD inclusion complexation against S. aureus and E. coli. In all these studies, HPbetaCD had superior antimicrobial activity than that of betaCD while betaCD had greater effect on solubility enhancement of CEF. PMID:18367363

Aleem, Omair; Kuchekar, Bhanudas; Pore, Yogesh; Late, Sameer

2008-07-15

309

High Beta Tokamaks  

SciTech Connect

Perhaps the ideal tokamak would have high {beta} ({beta} {approx}> 1) and classical confinement. Such a tokamak has not been found, and we do not know if one does exist. We have searched for such a possibility, so far without success. In 1990, we obtained analytic equilibrium solutions for large aspect ratio tokamaks at {beta} {approx} {Omicron}(1) [1]. These solutions and the extension at high {beta} poloidal to finite aspect ratio [2] provided a basis for the study of high {beta} tokamaks. We have shown that these configurations can be stable to short scale MHD modes [3], and that they have reduced neoclassical transport [4]. Microinstabilities (such as the {del}T{sub i} mode) seem to be stabilized at high {beta} [5] - this is due to the large local shear [3] and the magnetic well. We have some concerns about modes associated with the compressional branch which may appear at high {beta}. Bill Dorland and Mike Kotschenreuther have studied this issue and our concerns may be unfounded. It is certainly tantalizing, especially given the lowered neoclassical transport values, that these configurations could have no microinstabilities and, one could assume, no anomalous transport. Unfortunately, while this work is encouraging, the key question for high {beta} tokamaks is the stability to large scale kink modes. The MHD {beta} limit (Troyon limit) for kink modes at large aspect ratio is problematically low. There is ample evidence from computations that the limit exists. However, it is not known if stable equilibria exist at much higher {beta}--none have been found. We have explored this question in the asymptotic high {beta} poloidal limit. Unfortunately, we are unable to find stable equilibrium and also unable to show that they don't exist. The results of these calculations will be published when a more definitive answer is found.

Cowley, S.

1998-11-14

310

17. INTAKE PIER, BRIDGE STRESS SHEET, SHEET 8 OF 117, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

17. INTAKE PIER, BRIDGE STRESS SHEET, SHEET 8 OF 117, 1920. - Sacramento River Water Treatment Plant Intake Pier & Access Bridge, Spanning Sacramento River approximately 175 feet west of eastern levee on river; roughly .5 mile downstream from confluence of Sacramento & American Rivers, Sacramento, Sacramento County, CA

311

13. Photograph of sheet 1 (index and title sheet) of ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

13. Photograph of sheet 1 (index and title sheet) of the Indiana State Highway Commission repair plans of 1969 for the Cicott Street Bridge. Photograph of a 24' by 36' print made from microfilm in the archives of the Indiana Department of Transportation in Indianapolis. - Cicott Street Bridge, Spanning Wabash River at State Road 25, Logansport, Cass County, IN

312

9. Photograph of sheet 1 (index and title sheet) of ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

9. Photograph of sheet 1 (index and title sheet) of the State Highway Department of Indiana repair plans of 1957 for the Cicott Street Bridge. Photograph of a 24' by 36' print made from microfilm in the archives of the Indiana Department of Transportation in Indianapolis. - Cicott Street Bridge, Spanning Wabash River at State Road 25, Logansport, Cass County, IN

313

Engineering Research Center Fact Sheets  

NSDL National Science Digital Library

Curious about the latest developments in bioengineering, microelectronics, or earthquake hazard reduction? Wondering what type of research your tax dollars support? Then have a look at this recent posting from the National Science Foundation's (NSF's) Engineering Research Centers (ERC) Program which supports university research in partnership with industry. Here, users can access project descriptions from a variety of laboratories associated with the ERC. Examples of centers featured include Georgia Tech/ Emory Center for the Engineering of Living Tissues, Pacific Earthquake Engineering Research Center, Center for Neuromorphic Systems Engineering, and Center for Advanced Engineering Fibers and Films, to name a few. The research pages, available in either HTML or .pdf formats, present research goals, collaborating institutions, facility overviews, technology transfer initiatives, educational outreach projects, and links to contacts. At many of the pages, color photographs and illustrations accompany text. So the next time you are taking a break from work, peruse the NSF's Engineering Research Centers Fact Sheets and get the latest news about federally funded research and technology.

2001-01-01

314

The quantitative inspection of iron aluminide green sheet using transient thermography  

NASA Astrophysics Data System (ADS)

The recent development of manufacturing techniques for the fabrication of thin iron aluminide, FeAl, sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet, either by cold rolling or tape casting FeAl powder mixed with organic binding agents. The finished sheet is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. Previous work has demonstrated the advantages of using active thermography to detect the flaws and heterogeneity within green powder composites (1)(2)(3). The production environment and physical characteristics of these composites provide for unique challenges in developing a rapid nondestructive inspection capability. Thermography is non-contact and minimizes the potential damage to the fragile green sheet. Limited access to the material also demands a one-sided inspection technique. In this paper, we will describe the application of thermography for 100% on-line inspection within an industrial process. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The formation of green sheet flaws and their transformation into defects within intermediate and finished sheet products will be described. A green sheet conformance criterion will be presented which would significantly reduce the probability of processing poor quality green sheet which contributes to higher waste and inferior bulk alloy sheet.

Watkins, Michael L.; Hinders, Mark K.; Scorey, Clive; Winfree, William

1999-12-01

315

BETA GAUGE OPERATION MANUAL  

EPA Science Inventory

This manual provides description and operating instructions for a redesigned Beta Gauge for measuring particles from vehicle exhaust. The improvements and a new control system including a control unit which is radically different from the prior unit, are described. Complete Beta ...

316

Xenopus Egg Wnt/{beta}-Catenin Pathway  

NSDL National Science Digital Library

In embryonic development in vertebrates, &beta;-catenin signaling promotes polarization of the embryo to establish the dorsoventral axis, and it is this process that is highlighted by the Xenopus Egg Wnt/&beta;-Catenin Pathway. In the amphibian Xenopus, fertilization of the egg results in the establishment of a parallel array of microtubules with the plus end pointing away from the sperm entry point. Concurrent with a process of cortical rotation, in which the cortex of the egg utilizes these microtubules to rotate relative to the inner cytoplasm, there is a movement of small vesicles toward the plus end of the microtubules. Cells inheriting these vesicles are destined to give rise to dorsal and anterior structures of the embryo. Three components of the Wnt/&beta;-catenin pathway—Dishevelled, glycogen synthase kinase 3 (GSK-3)-binding protein (GBP), and &beta;-catenin—accumulate on the side of the egg and early embryo that receive these small vesicles. It is likely that Dishevelled and GBP are associated with the vesicles that move along the microtubules and that they promote the stabilization and dorsal accumulation of &beta;-catenin. Although Wnts and Frizzled are present in the egg, their roles in axis specification remain unclear. Dorsal &beta;-catenin then activates direct target genes, including the homeobox genes siamois and twinned. Activation of these genes on the prospective dorsal side is necessary and sufficient for formation of the gastrula organizer, which organizes the embryonic germ layers and axes.

Randall T. Moon (University of Washington School of Medicine;HHMI and Center for Developmental Biology REV)

2005-02-15

317

The Rapid Ice Sheet Change Observatory (RISCO)  

NASA Astrophysics Data System (ADS)

The recent expansion of observational capacity from space has revealed dramatic, rapid changes in the Earth’s ice cover. These discoveries have fundamentally altered how scientists view ice-sheet change. Instead of just slow changes in snow accumulation and melting over centuries or millennia, important changes can occur in sudden events lasting only months, weeks, or even a single day. Our understanding of these short time- and space-scale processes, which hold important implications for future global sea level rise, has been impeded by the low temporal and spatial resolution, delayed sensor tasking, incomplete coverage, inaccessibility and/or high cost of data available to investigators. New cross-agency partnerships and data access policies provide the opportunity to dramatically improve the resolution of ice sheet observations by an order of magnitude, from timescales of months and distances of 10’s of meters, to days and meters or less. Advances in image processing technology also enable application of currently under-utilized datasets. The infrastructure for systematically gathering, processing, analyzing and distributing these data does not currently exist. Here we present the development of a multi-institutional, multi-platform observatory for rapid ice change with the ultimate objective of helping to elucidate the relevant timescales and processes of ice sheet dynamics and response to climate change. The Rapid Ice Sheet Observatory (RISCO) gathers observations of short time- and space-scale Cryosphere events and makes them easily accessible to investigators, media and general public. As opposed to existing data centers, which are structured to archive and distribute diverse types of raw data to end users with the specialized software and skills to analyze them, RISCO focuses on three types of geo-referenced raster (image) data products in a format immediately viewable with commonly available software. These three products are (1) sequences of images and image animations from the ice sheet scale down to scales of meters, (2) maps of ice flow velocity and acceleration and (3) digital elevation models and elevation change maps. These products are created both from user-tasked data acquisitions and from a decade of archived data. An online user interface will allow browsing of the data catalog, product ordering and requests for sensor tasking. Over the next few years, RISCO will develop into a long-term observational system, with an adaptable infrastructure to accommodate new sensors and currently unforeseeable demands. RISCO has the potential to greatly enhance observation of ice sheets, moving from ad hoc studies of past changes using whatever data happens to be available, to scalable, targeted, near-real time monitoring of events as they occur.

Morin, P.; Howat, I. M.; Ahn, Y.; Porter, C.; McFadden, E. M.

2010-12-01

318

Texture Development and Drawability of Frictionally Rolled AA 5052 AL Alloy Sheet  

NASA Astrophysics Data System (ADS)

The microstructure, pole figure and r-value of the frictionally rolled and subsequently heat treated AA 5052 Al sheets were investigated by optical microscopy, x-ray diffractometer and tensile tester, respectively. Frictionally rolled AA 5052 Al specimens showed a fine grain size. After subsequently heat treated specimens, the ND//<111> texture component was increased. The r-values of the frictionally rolled and subsequently heat treated Al alloy sheets were about two times higher than those of the original Al sheets. These could be related to the formation of ND//<111> texture components through frictional rolling in and subsequent heat treatment of AA 5052 Al sheet.

Kim, Insoo; Akramov, Saidmurod; Jeong, Hae Bong; No, Tae Kyoung

319

Applied beta dosimetry  

SciTech Connect

The science or art of beta dosimetry is as old as the Nuclear Industry itself but still is poorly understood. Many practicing health physicists have thought the detection, measurement, and evaluation of beta dose and/or dose rates to be a solved problem, accepting reported field survey readings and personnel dose measurements at face value. However, beta doses (primarily a skin dose), if measured at all, are generally inaccurate at best. Field measurements of beta-gamma dose rates are equally difficult, and estimation of personnel dosimeter results from field surveys have proven to be suprising, frustrating, and risky. Beta calibration sources have not been available in the intensity and energy ranges needed and, in general, have not been adequately characterized for either intensity or energy spectra vs distance. The purposes of this report are to discuss the current industry capabilities, highlighting pitfalls for the applied health physics personnel, and briefly outlining preferred practices.

Rich, B.L.

1982-06-01

320

Writing by Number: Teaching Students to Read the Balance Sheet.  

ERIC Educational Resources Information Center

Describes an assignment in which students write a short memo report analyzing and comparing both what a company says in its annual report and what its balance sheet shows. Describes four simple mathematical formulas students can use to quickly diagnose a company's financial health. Appends a sample of the short report format. (RS)

Cross, Mary

1990-01-01

321

MIXED DOUBLES TENNIS Information Sheet  

E-print Network

MIXED DOUBLES TENNIS Information Sheet Fall 2013 This information sheet is intended to provide will be played at the SFH Indoor Tennis Courts. CHECK-IN It is recommended that participants check for the intramural activity fee at their first match. EQUIPMENT Each team must provide tennis balls (preferably new

Seamons, Kent E.

322

MIXED DOUBLES TENNIS Information Sheet  

E-print Network

MIXED DOUBLES TENNIS Information Sheet Winter 2014 This information sheet is intended to provide:00-10:00 PM and Saturday from 12:00-6:00 PM in the SFH Indoor Tennis Courts. CHECK-IN It is recommended their rackets and a can of tennis balls. It is strongly recommended that the tennis balls are new. Equipment may

Seamons, Kent E.

323

Beta-ensembles with covariance  

E-print Network

This thesis presents analytic samplers for the [beta]-Wishart and [beta]-MANOVA ensembles with diagonal covariance. These generalize the [beta]-ensembles of Dumitriu-Edelman, Lippert, Killip-Nenciu, Forrester-Rains, and ...

Dubbs, Alexander

2014-01-01

324

CURRENT SHEETS AND COLLISIONLESS DAMPING IN KINETIC PLASMA TURBULENCE  

SciTech Connect

We present the first study of the formation and dissipation of current sheets at electron scales in a wave-driven, weakly collisional, three-dimensional kinetic turbulence simulation. We investigate the relative importance of dissipation associated with collisionless damping via resonant wave-particle interactions versus dissipation in small-scale current sheets in weakly collisional plasma turbulence. Current sheets form self-consistently from the wave-driven turbulence, and their filling fraction is well correlated to the electron heating rate. However, the weakly collisional nature of the simulation necessarily implies that the current sheets are not significantly dissipated via Ohmic dissipation. Rather, collisionless damping via the Landau resonance with the electrons is sufficient to account for the measured heating as a function of scale in the simulation, without the need for significant Ohmic dissipation. This finding suggests the possibility that the dissipation of the current sheets is governed by resonant wave-particle interactions and that the locations of current sheets correspond spatially to regions of enhanced heating.

TenBarge, J. M.; Howes, G. G., E-mail: jason-tenbarge@uiowa.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States)

2013-07-10

325

Vertically scanned laser sheet microscopy.  

PubMed

Laser sheet microscopy is a widely used imaging technique for imaging the three-dimensional distribution of a fluorescence signal in fixed tissue or small organisms. In laser sheet microscopy, the stripe artifacts caused by high absorption or high scattering structures are very common, greatly affecting image quality. To solve this problem, we report here a two-step procedure which consists of continuously acquiring laser sheet images while vertically displacing the sample, and then using the variational stationary noise remover (VSNR) method to further reduce the remaining stripes. Images from a cleared murine colon acquired with a vertical scan are compared with common stitching procedures demonstrating that vertically scanned light sheet microscopy greatly improves the performance of current light sheet microscopy approaches without the need for complex changes to the imaging setup and allows imaging of elongated samples, extending the field of view in the vertical direction. PMID:25271539

Dong, Di; Arranz, Alicia; Zhu, Shouping; Yang, Yujie; Shi, Liangliang; Wang, Jun; Shen, Chen; Tian, Jie; Ripoll, Jorge

2014-10-01

326

TGF-beta1, IL-1beta, and Th2 cytokines stimulate vascular endothelial growth factor production from conjunctival fibroblasts.  

PubMed

Giant papillary formation containing newly formed vessels is a major characteristic of severe allergic conjunctivitis, such as atopic keratoconjunctivitis (AKC) or vernal keratoconjunctivitis (VKC). We examined production of vascular endothelial growth factor (VEGF) from cultured conjunctival fibroblasts from normal volunteers under stimulation with type 1-, type 2-helper T cell derived and proinflammatory cytokines to investigate the mechanism of giant papillae formation in AKC/VKC. Primary cultured conjunctival fibroblasts were incubated with interleukin (IL)-4, IL-13, IL-1beta, IL-2, tumor necrotizing factor (TNF)-alpha, interferon (IFN)-gamma, or transforming growth factor (TGF)-beta1. Effects of cytokines on VEGF protein secretion in supernatant were assessed by ELISA, and VEGF mRNA expression in cultured cells were assessed by quantitative PCR. TGF-beta1 most effectively increased VEGF concentration with dose- and time-dependent manner IL-1beta, IL-4, and IL-13 significantly increased VEGF concentration. Though IL-2 also showed slight increase of VEGF concentration, it was not statistically significant. TNF-alpha and INF-gamma did not increase VEGF concentration. Quantitative PCR showed significant increase of VEGF mRNA in TGF-beta1, IL-1beta, and IL-4 stimulated fibroblasts. TGF-beta1, IL-1beta, and Th2 cytokines from allergic inflammatory cells induced VEGF production in conjunctival fibroblasts, and may play a crucial role in neovascularization and formation of giant papillae in AKC/VKC. PMID:15781283

Asano-Kato, Naoko; Fukagawa, Kazumi; Okada, Naoko; Kawakita, Tetsuya; Takano, Yoji; Dogru, Murat; Tsubota, Kazuo; Fujishima, Hiroshi

2005-04-01

327

Galvanized Sheet Metal Lab  

NSDL National Science Digital Library

This module, created by Jamie Acker of Olympic High School in Bremerton, Washington, provides a look into an entry-level lab on galvanized metal. The introduction states, "This simple lab visually shows the effects of removing zinc from a galvanized piece of sheet metal and provides students an opportunity to mathematically calculate the reduction in thickness of the zinc and number of atoms lost, based on the change in mass." The module features an abstract, objective, curriculum overview, procedures, mathematical calculations and references. Students should gain knowledge taking measurements using a micrometer/beam balance, how to safely handle strong acids and use algebra to rearrange equations to balance equations. This is a great resource to either enhance or create new curriculum for instructors.

Acker, Jamie

2009-09-30

328

Current Sheet Properties and Dynamics During Sympathetic Breakout Eruptions  

NASA Astrophysics Data System (ADS)

We present the continued analysis of the high-resolution 2.5D MHD simulations of sympathetic magnetic breakout eruptions from a pseudostreamer source region. We examine the generation of X- and O-type null points during the current sheet tearing and track the magnetic island formation and evolution during periods of reconnection. The magnetic breakout eruption scenario forms an overlying 'breakout' current sheet that evolves slowly and removes restraining flux from above the sheared field core that will eventually become the center of the erupting flux rope-like structure. The runaway expansion from the expansion-breakout reconnection positive feedback enables the formation of the second, vertical/radial current sheet underneath the rising sheared field core as in the standard CHSKP eruptive flare scenario. We will examine the flux transfer rates through the breakout and flare current sheets and compare the properties of the field and plasma inflows into the current sheets and the reconnection jet outflows into the flare loops and flux rope ejecta.

Lynch, B. J.; Edmondson, J. K.

2013-12-01

329

Ganges Chasma Sand Sheet  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

Today's sand sheet is located in the Ganges Chasma portion of Valles Marineris. As with yesterday's image, note that the dune forms are seen only at the margin and that the interior of the sand sheet at this resolution appears to completely lack dune forms.

Image information: VIS instrument. Latitude -6.4, Longitude 310.7 East (49.3 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2005-01-01

330

Wavefront shaping of a Bessel light field enhances light sheet microscopy with scattered light  

NASA Astrophysics Data System (ADS)

Light sheet microscopy has seen a resurgence as it facilitates rapid, high contrast, volumetric imaging with minimal sample exposure. Initially developed for imaging scattered light, this application of light sheet microscopy has largely been overlooked but provides an endogenous contrast mechanism which can complement fluorescence imaging and requires very little or no modification to an existing light sheet fluorescence microscope. Fluorescence imaging and scattered light imaging differ in terms of image formation. In the former the detected light is incoherent and weak whereas in the latter the coherence properties of the illumination source, typically a laser, dictate the coherence of detected light, but both are dependent on the quality of the illuminating light sheet. Image formation in both schemes can be understood as the convolution of the light sheet with the specimen distribution. In this paper we explore wavefront shaping for the enhancement of light sheet microscopy with scattered light. We show experimental verification of this result, demonstrating the use of the propagation invariant Bessel beam to extend the field of view of a high resolution scattered light, light sheet microscope and its application to imaging of biological super-cellular structures with sub-cellular resolution. Additionally, complementary scattering and fluorescence imaging is used to characterize the enhancement, and to develop a deeper understanding of the differences of image formation between contrast mechanisms in light sheet microscopy.

Nylk, J.; Mitchell, C.; Vettenburg, T.; Gunn-Moore, F. J.; Dholakia, K.

2014-03-01

331

Effects of au plating on small-scale resistance spot welding of thin-sheet nickel  

Microsoft Academic Search

The effects of Au plating on joint formation and joint strength in small-scale resistance spot welding (SSRSW) of Ni sheets\\u000a have been investigated using tensile-shear testing, optical microscopy, scanning electron microscopy (SEM), and energy-dispersive\\u000a X-ray spectroscopy (EDX). The results show that the mechanisms of the joint formation during the welding of Au-plated Ni sheets\\u000a involve solid-state bonding, brazing, and fusion

W. Tan; Y. Zhou; H. W. Kerr

2002-01-01

332

Creation of prompt and thin-sheet splashing by varying surface roughness or increasing air pressure  

E-print Network

A liquid drop impacting a solid surface may splash by emitting a thin liquid sheet that subsequently breaks apart or by promptly ejecting droplets from the advancing liquid-solid contact line. Using high-speed imaging, we show that air pressure and surface roughness influence both splash mechanisms. Roughness increases prompt splashing at the advancing contact line but inhibits the formation of the thin sheet. If the air pressure is lowered, droplet ejection is suppressed not only during thin-sheet formation but for prompt splashing as well. The threshold pressure depends on impact velocity, liquid viscosity and surface roughness.

Latka, Andrzej; Driscoll, Michelle M; Stevens, Cacey S; Nagel, Sidney R

2012-01-01

333

Snail and Slug promote epithelial-mesenchymal transition through beta-catenin-T-cell factor-4-dependent expression of transforming growth factor-beta3.  

PubMed

Members of the Snail family of transcription factors have been shown to induce epithelial-mesenchymal transition (EMT), a fundamental mechanism of embryogenesis and progressive disease. Here, we show that Snail and Slug promote formation of beta-catenin-T-cell factor (TCF)-4 transcription complexes that bind to the promoter of the TGF-beta3 gene to increase its transcription. Subsequent transforming growth factor (TGF)-beta3 signaling increases LEF-1 gene expression causing formation of beta-catenin-lymphoid enhancer factor (LEF)-1 complexes that initiate EMT. TGF-beta1 or TGF-beta2 stimulates this signaling mechanism by up-regulating synthesis of Snail and Slug. TGF-beta1- and TGF-beta2-induced EMT were found to be TGF-beta3 dependent, establishing essential roles for multiple TGF-beta isoforms. Finally, we determined that beta-catenin-LEF-1 complexes can promote EMT without upstream signaling pathways. These findings provide evidence for a unified signaling mechanism driven by convergence of multiple TGF-beta and TCF signaling molecules that confers loss of cell-cell adhesion and acquisition of the mesenchymal phenotype. PMID:18799618

Medici, Damian; Hay, Elizabeth D; Olsen, Bjorn R

2008-11-01

334

Curvature effects of nitrogen on graphitic sheets: Structures and energetics  

NASA Astrophysics Data System (ADS)

A correlation of the nitrogen concentration on graphitic sheets with structural deformations is presented using the density functional based tight binding method (DFTB). Graphite sheets of various sizes were doped by nitrogen at different sites; either a local deviation from planarity or negative curvature is obtained. In addition, we derive a formula for constructing two sets of isomer series namely methylene cyclopentadiene and benzene to study nitrogen's role in positive curvature formation. Comparing these structures, the exact energy difference to convert a fully hexagonal network to a pentagon centered hexagonal network can be predicted systematically for infinitely large structures.

Mandumpal, Jestin; Gemming, Sibylle; Seifert, Gotthard

2007-10-01

335

Beta barium borate (BBO)  

Microsoft Academic Search

The paper contains a review of crystallographic, optical and nonlinear optical properties of beta barium borate (ß-BaB2O4 or BBO) crystal and presents a description of its typical applications in nonlinear optics and quantum electronics.

D. N. Nikogosyan

1991-01-01

336

Neutrinoless double beta decay  

E-print Network

The physics potential of neutrinoless double beta decay is discussed. Furthermore, experimental considerations are presented as well as the current status of experiments. Finally an outlook towards the future, work on nuclear matrix elements and alternative processes is given.

K. Zuber

2012-01-23

337

Beta blockers overdose  

MedlinePLUS

... used to treat high blood pressure. Beta blocker overdose occurs when someone accidentally or intentionally takes more ... is common in children with this type of overdose, and it can lead to nervous system symptoms.

338

Beta Estimate Experiment  

NSDL National Science Digital Library

This resource consists of a Java applet and expository text. The applet simulates a random sample from a beta distribution, and computes standard point estimates of the left and right parameters. The bias and mean square error are also computed.

Siegrist, Kyle

339

Beta-thalassemia  

Microsoft Academic Search

Beta-thalassemias are a group of hereditary blood disorders characterized by anomalies in the synthesis of the beta chains of hemoglobin resulting in variable phenotypes ranging from severe anemia to clinically asymptomatic individuals. The total annual incidence of symptomatic individuals is estimated at 1 in 100,000 throughout the world and 1 in 10,000 people in the European Union. Three main forms

Renzo Galanello; Raffaella Origa

2010-01-01

340

ICQ 2000b Beta  

NSDL National Science Digital Library

The latest beta release of the universally popular instant messaging program ICQ ("I seek you") contains a number of new features, including ICQphone, which makes it possible for users to initiate and participate in PC-to-PC and PC-to-Phone calls, support for SMS technology, integration with Outlook, and email address import, among others. Users can download ICQ 2000b Beta for free at the ICQ site.

2001-01-01

341

Nomination Form and Information Sheet  

E-print Network

Nomination Form and Information Sheet Name: Department: College: Phone: Email: Name of nominator Scholarship and Awards Teaching, Learning and Academic Resources Collective Agreement Committees: University be a member of Council) Senate Roundtable on Outreach and Engagement Recreation and Athletics Advisory

Saskatchewan, University of

342

Sheet Music From Canada's Past  

NSDL National Science Digital Library

If you love Canadian history and music, you will most find this site most fetching. Created by the Library and Archives Canada, the site brings together intriguing and historically important sheet music from the past 150 years. The collection exists due to the diligence of Helmut Kallmann, a young CBC music librarian who began to collect sheet music in the early 1950s. Today, the archives contain over 20,000 pieces of sheet music, many of which are available online. In addition, the site offers a handful of musical clips that represent pre-1921 Canadian musicality. Visitors can Search Sheet Music to get started or browse the Gallery area. Here visitors can look around via themes, including Colleges, Flowers, Summer Sports, and Winter. It is worth noting that although we reviewed the English site, the archives are also available in French.

343

Analysis of a Sheet Silicate.  

ERIC Educational Resources Information Center

Describes a student project in analytical chemistry using sheet silicates. Provides specific information regarding the use of phlogopite in an experiment to analyze samples for silicon, aluminum, magnesium, iron, potassium, and fluoride. (CS)

Adams, J. M.; Evans, S.

1980-01-01

344

FDTD modeling of thin impedance sheets  

NASA Technical Reports Server (NTRS)

Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.

Luebbers, Raymond J.; Kunz, Karl S.

1991-01-01

345

Analysis of instabilities in liquid sheets  

Microsoft Academic Search

Numerical and analytical solutions are presented for liquid sheets in order to confirm linearized predictions for inviscid flow and to investigate the transition to instability. Two sheet configurations are investigated. The first is a radially expanding sheet formed by impinging jets. Incompressible flow solutions are found for these sheets using an hp-finite element method. We observe that forced sinuous pulses

Nathaniel S. Barlow

2009-01-01

346

Systematic study of plasma flow during plasma sheet thinnings  

NASA Technical Reports Server (NTRS)

On the basis of a study of Imp 6 measurements of plasma flow, it is concluded that there is no clear indication of a predominance of tailward plasma flow beyond about X = -15 R sub E in the midnight sector of the plasma sheet during the expansive phase of a substorm. In fact, it is shown statistically that sunward plasma flow is more frequently observed in the midnight sector within about 30 R sub E from the earth than in any other direction during plasma sheet thinning at the substorm expansion. This result supports the conclusion that there is no definite evidence for the formation of a reconnection neutral line in the near-earth plasma sheet during most substorms.

Lui, A. T. Y.; Frank, L. A.; Ackerson, K. L.; Meng, C.-I.; Akasofu, S.-I.

1977-01-01

347

FDTD modeling of thin impedance sheets  

NASA Technical Reports Server (NTRS)

Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. It is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods. These sheets are characterized by a discontinuity in the tangential magnetic field on either side of the sheet but no discontinuity in tangential electric field. This continuity, or single valued behavior of the electric field, allows the sheet current to be expressed in terms of an impedance multiplying this electric field.

Luebbers, Raymond; Kunz, Karl

1991-01-01

348

FDTD modeling of thin impedance sheets  

NASA Astrophysics Data System (ADS)

Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. It is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods. These sheets are characterized by a discontinuity in the tangential magnetic field on either side of the sheet but no discontinuity in tangential electric field. This continuity, or single valued behavior of the electric field, allows the sheet current to be expressed in terms of an impedance multiplying this electric field.

Luebbers, Raymond; Kunz, Karl

349

Magnetic Reconnection in the Solar Wind at Current Sheets Associated with Extremely Small Field Shear Angles  

NASA Astrophysics Data System (ADS)

Using Wind 3-s plasma and magnetic field data, we have identified three reconnection exhausts within a large magnetic flux rope embedded within an interplanetary coronal mass ejection in the solar wind on 19 October 1998. These exhausts were associated with current sheets having local field shear angles ranging from 4.1 to 9.3 degrees, the smallest field shear angles (strongest guide fields) yet associated with identified reconnection exhausts in a space plasma. They were observed in plasma characterized by extremely low (<0.01) proton beta and very high (281 - 383 km/s) Alfvén speed. The very low external plasma beta in these events minimized the effect of diamagnetic drift of the X-line and thus allowed reconnection to occur in a sustained fashion. And, the very high external Alfvén speed translated into sufficiently fast (> 10 km/s) exhaust jets that could be adequately resolved by the Wind 3DP plasma experiment. Thin, very small field shear-angle current sheets are common in the solar wind, but typically are not associated with particularly low plasma beta or particularly high Alfvén speeds. On the other hand, small field shear angle current sheets must also be dominant in topologically complex environments such as the solar corona where the plasma beta is often less than 0.01 and the Alfvén speed is high. Our observations thus suggest that reconnection at thin, low field shear angle current sheets should commonly occur in the corona, and lend some credence to models that suggest that reconnection at low field shear angle current sheets contributes substantially to coronal heating.

Gosling, J. T.; Phan, T. D.

2012-12-01

350

Global ice-sheet system interlocked by sea level  

SciTech Connect

Denton and Hughes postulated that sea level linked a global ice-sheet system with both terrestrial and grounded marine components during later Quaternary ice ages. Summer temperature changes near Northern Hemisphere melting margins initiated sea-level fluctuations that controlled marine components in both polar hemispheres. It was further proposed that variations of this ice-sheet system amplified and transmitted Milankovitch summer half-year insolation changes between 45 and 75/sup 0/N into global climatic changes. New tests of this hypothesis implicate sea level as a major control of the areal extent of grounded portions of the Antarctic Ice Sheet. But factors other than areal changes of the grounded Antarctic Ice Sheet may have strongly influenced Southern Hemisphere climate and terminated the last ice age simultaneously in both polar hemispheres. Atmospheric carbon dioxide linked to high-latitude oceans is the most likely candidate, but another potential influence was high-frequency climatic oscillations. It is postulated that variations in atmospheric carbon dioxide acted through an Antarctic ice shelf linked to the grounded ice sheet to produce and terminate Southern Hemisphere ice-age climate. It is further postulated that Milankovitch summer insolation combined with a warm-high frequency oscillation caused marked recession of Northern Hemisphere ice-sheet melting margins and the North Atlantic polar front about 14,000 /sup 14/C yr B.P. This permitted renewed formation of North Atlantic Deep Water, which could well have controlled atmospheric carbon dioxide. Combined melting and consequent sea-level rise from the three warming factors initiated irreversible collapse of the interlocked global ice-sheet system, which was at its largest but most vulnerable configuration.

Denton, G.H.; Hughes, T.J.; Karlen, W.

1986-01-01

351

Amyloid Beta as a Modulator of Synaptic Plasticity  

PubMed Central

Alzheimer’s disease is associated with synapse loss, memory dysfunction and pathological accumulation of amyloid beta in plaques. However, an exclusively pathological role for amyloid beta is being challenged by new evidence for an essential function of amyloid beta at the synapse. Amyloid beta protein exists in different assembly states in the central nervous system and plays distinct roles ranging from synapse and memory formation to memory loss and neuronal cell death. Amyloid beta is present in the brain of symptom-free people where it likely performs important physiological roles. New evidence indicates that synaptic activity directly evokes the release of amyloid beta at the synapse. At physiological levels, amyloid beta is a normal, soluble product of neuronal metabolism that regulates synaptic function beginning early in life. Monomeric amyloid beta 40 and 42 are the predominant forms required for synaptic plasticity and neuronal survival. With age, some assemblies of amyloid beta are associated with synaptic failure and Alzheimer’s disease pathology, possibly targeting the N-methyl-D-aspartic acid (NMDA) receptor through the ?7-nicotinic acetylcholine receptor (?7-nAChR), mitochondrial amyloid-? alcohol dehydrogenase (ABAD) and cyclophilin D. But emerging data suggests a distinction between age effects on the target response in contrast to the assembly state or the accumulation of the peptide. Both aging and beta amyloid independently decrease neuronal plasticity. Our laboratory has reported that amyloid beta, glutamate and lactic acid are each increasingly toxic with neuron age. The basis of the age-related toxicity partly resides in age-related mitochondrial dysfunction and an oxidative shift in mitochondrial and cytoplasmic redox potential. In turn, signaling through phosphorylated extracellular signal-regulated protein kinases (pERK) is affected along with an age-independent increase in phosphorylated cAMP response element-binding protein (pCREB) This review examines the long-awaited functional impact of amyloid beta on synaptic plasticity. PMID:20847424

Parihar, Mordhwaj S; Brewer, Gregory J

2011-01-01

352

Windows Media Player 6.2 Beta  

NSDL National Science Digital Library

With the Windows Media Player 6.2 Beta, Microsoft enters the high quality, compressed digital music fray. Not only does Microsoft's new media player support numerous media formats, but it also has several novel features. It supports the new MS Audio 4.0 format, which claims to provide MP3-quality sound at half the size of MP3 files, and it offers "intelligent streaming," which increases the probability of a smooth streamed media experience. Somewhat less wonderful for the end-user may be its support for the Windows Media Rights Manager, which provides piracy protection and license control. Though similar to RealPlayer, the Windows Media Player 6.2 Beta's interesting and unique features make it worth checking out. The player runs on Win95/98/NT and is free to download and use.

353

Manufacturing Laboratory (Fact Sheet)  

SciTech Connect

This fact sheet describes the purpose, lab specifications, applications scenarios, and information on how to partner with NREL's Manufacturing Laboratory at the Energy Systems Integration Facility. The Manufacturing Laboratory at NREL's Energy Systems Integration Facility (ESIF) focuses on developing methods and technologies that will assist manufacturers of hydrogen and fuel cell technologies, as well as other renewable energy technologies, to scale up their manufacturing capabilities to volumes that meet DOE and industry targets. Specifically, the manufacturing activity is currently focused on developing and validating quality control techniques to assist manufacturers of low temperature and high temperature fuel cells in the transition from low to high volume production methods for cells and stacks. Capabilities include initial proof-of-concept studies through prototype system development and in-line validation. Existing diagnostic capabilities address a wide range of materials, including polymer films, carbon and catalyst coatings, carbon fiber papers and wovens, and multi-layer assemblies of these materials, as well as ceramic-based materials in pre- or post-fired forms. Work leading to the development of non-contact, non-destructive techniques to measure critical dimensional and functional properties of fuel cell and other materials, and validation of those techniques on the continuous processing line. This work will be supported by materials provided by our partners. Looking forward, the equipment in the laboratory is set up to be modified and extended to provide processing capabilities such as coating, casting, and deposition of functional layers, as well as associated processes such as drying or curing. In addition, continuous processes are used for components of organic and thin film photovoltaics (PV) as well as battery technologies, so synergies with these important areas will be explored.

Not Available

2011-10-01

354

Toxicological Profile Information Sheet  

NSDL National Science Digital Library

The Agency for Toxic Substances and Disease Registry (ATSDR) is continually assembling toxicological profiles for hazardous substances. This site contains 256 online profiles listed alphabetically by chemical name. Each profile begins with a non-technical public health statement discussing the chemical, its environmental and health effects, and risk of human exposure. A more technical version of this information can also be downloaded in Adobe Acrobat (.pdf) format.

2001-01-01

355

Unfolding of ?-Sheet Proteins in SDS  

PubMed Central

?-Sheet proteins are particularly resistant to denaturation by sodium dodecyl sulfate (SDS). Here we compare unfolding of two ?-sandwich proteins TNfn3 and TII27 in SDS. The two proteins show different surface electrostatic potential. Correspondingly, TII27 unfolds below the critical micelle concentration via the formation of hemimicelles on the protein surface, whereas TNfn3 only unfolds around the critical micelle concentration. Isothermal titration calorimetry confirms that unfolding of TII27 sets in at lower SDS concentrations, although the total number of bound SDS molecules is similar at the end of unfolding. In mixed micelles with the nonionic detergent dodecyl maltoside, where the concentration of monomeric SDS is insignificant, the behavior of the two proteins converges. TII27 unfolds more slowly than TNfn3 in SDS and follows a two-mode behavior. Additionally TNfn3 shows inhibition of SDS unfolding at intermediate SDS concentrations. Mutagenic analysis suggests that the overall unfolding mechanism is similar to that observed in denaturant for both proteins. Our data confirm the kinetic robustness of ?-sheet proteins toward SDS. We suggest this is related to the inability of SDS to induce significant amounts of ?-helix structure in these proteins as part of the denaturation process, forcing the protein to denature by global rather than local unfolding. PMID:17351005

Nielsen, Mette M.; Andersen, Kell K.; Westh, Peter; Otzen, Daniel E.

2007-01-01

356

Nuclear Data Sheets for A = 178  

SciTech Connect

The present revision of the nuclear structure properties for the nuclides belonging to the A = 178 mass chain contains many improvements and additions to the material presented in the previous evaluation (1994Br18, Nucl. Data Sheets 72, 221 (1994)). Besides updating many values, and including supplementary data for already known levels, transitions and level schemes, the most noteworthy modifications with respect to the prior evaluation are extensive additions to the level schemes of {sup 178}Yb, {sup 178}Hf, {sup 178}Ta, {sup 178}W. {sup 178}Ir, {sup 178}Pt and {sup 178}Hg, based on HI reaction works performed after the last cutoff date (July 1993), and to {sup 178}Hf due to new data from recent Coulomb excitation experiments. Light ion ({sup 3}He, {alpha}) beam experiments have added many data for {sup 178}Ta. Beta decay studies have also provided significant data for {sup 178}W and {sup 178}Pt. Lastly the first report of the identification of {sup 178}Tl and {sup 178}Pb is included.

Achterberg, E.; Capurro, O.A.; Marti, G.V. [Laboratorio TANDAR, Departamento de Fisica, Comision Nacional de Energia Atomica, Buenos Aires (Argentina)

2009-07-15

357

Digitalis purpurea P5 beta R2, encoding steroid 5 beta-reductase, is a novel defense-related gene involved in cardenolide biosynthesis.  

PubMed

The stereospecific 5 beta-reduction of progesterone is a required step for cardiac glycoside biosynthesis in foxglove plants. Recently, we have isolated the gene P5 beta R, and here we investigate the function and regulation of P5 beta R2, a new progesterone 5 beta-reductase gene from Digitalis purpurea. P5 beta R2 cDNA was isolated from a D. purpurea cDNA library and further characterized at the biochemical, structural and physiological levels. Like P5 beta R, P5 beta R2 catalyzes the 5 beta-reduction of the Delta(4) double bond of several steroids and is present in all plant organs. Under stress conditions or on treatment with chemical elicitors, P5 beta R expression does not vary, whereas P5 beta R2 is highly responsive. P5 beta R2 expression is regulated by ethylene and hydrogen peroxide. The correlation between P5 beta R2 expression and cardenolide formation demonstrates the key role of this gene in cardenolide biosynthesis, and therefore in the chemical defense of foxglove plants. PMID:19895417

Pérez-Bermúdez, Pedro; García, Aurelio A Moya; Tuñón, Iñaki; Gavidia, Isabel

2010-02-01

358

Transforming growth factor-beta activation in irradiated murine mammary gland.  

PubMed Central

The biological activity of TGF-beta, an important modulator of cell proliferation and extracellular matrix formation, is governed by dissociation of mature TGF-beta from an inactive, latent TGF-beta complex in a process that is critical to its role in vivo. So far, it has not been possible to monitor activation in vivo since conventional immunohistochemical detection does not accurately discriminate latent versus active TGF-beta, nor have events associated with activation been defined well enough to serve as in situ markers of this process. We describe here a modified immunodetection method using differential antibody staining that allows the specific detection of active versus latent TGF-beta. Under these conditions, we report that an antibody raised to latency-associated peptide detects latent TGF-beta, and we demonstrate that LC(1-30) antibodies specifically recognize active TGF-beta 1 in tumor xenografts overproducing active TGF-beta 1, without cross-reactivity in tumors expressing similar levels of latent TGF-beta 1. We previously reported that TGF-beta immunoreactivity increases in murine mammary gland after whole-body 60Co-gamma radiation exposure. Using differential antibody staining we now show that radiation exposure specifically generates active TGF-beta 1. While latent TGF-beta 1 was widely distributed in unirradiated tissue, active TGF-beta 1 distribution was restricted. Active TGF-beta 1 increased significantly within 1 h of irradiation concomitant with decreased latent TGF-beta immunoreactivity. This rapid shift in immunoreactivity provides the first evidence for activation of TGF-beta in situ. This reciprocal pattern of expression persisted for 3 d and was accompanied by decreased recovery of latent TGF-beta 1 from irradiated tissue. Radiation-induced activation of TGF-beta may have profound implications for understanding tissue effects caused by radiation therapy. Images PMID:8113421

Barcellos-Hoff, M H; Derynck, R; Tsang, M L; Weatherbee, J A

1994-01-01

359

Structure of bacterial 3beta/17beta-hydroxysteroid dehydrogenase at 1.2 A resolution: a model for multiple steroid recognition.  

PubMed

The enzyme 3beta/17beta-hydroxysteroid dehydrogenase (3beta/17beta-HSD) is a steroid-inducible component of the Gram-negative bacterium Comamonas testosteroni. It catalyzes the reversible reduction/dehydrogenation of the oxo/beta-hydroxy groups at positions 3 and 17 of steroid compounds, including hormones and isobile acids. Crystallographic analysis at 1.2 A resolution reveals the enzyme to have nearly identical subunits that form a tetramer with 222 symmetry. This is one of the largest oligomeric structures refined at this resolution. The subunit consists of a monomer with a single-domain structure built around a seven-stranded beta-sheet flanked by six alpha-helices. The active site contains a Ser-Tyr-Lys triad, typical for short-chain dehydrogenases/reductases (SDR). Despite their highly diverse substrate specificities, SDR members show a close to identical folding pattern architectures and a common catalytic mechanism. In contrast to other SDR apostructures determined, the substrate binding loop is well-defined. Analysis of structure-activity relationships of catalytic cleft residues, docking analysis of substrates and inhibitors, and accessible surface analysis explains how 3beta/17beta-HSD accommodates steroid substrates of different conformations. PMID:12475215

Benach, Jordi; Filling, Charlotta; Oppermann, Udo C T; Roversi, Pietro; Bricogne, Gérard; Berndt, Kurt D; Jörnvall, Hans; Ladenstein, Rudolf

2002-12-17

360

Structure of the hormone binding domain of human beta 1 thyroid hormone nuclear receptor: is it an alpha/beta barrel?  

PubMed

To understand the structure of the hormone binding domain (HBD) of human beta 1 thyroid hormone nuclear receptor (h-TR beta 1), truncated h-TR beta 1 fragments, MD32 (M169-D456), KD29 (K201-D456), DD28 (D211-D456), KD25 (K235-D456), and KP28 (K201-P448), were analyzed by circular dichorism (CD). MD32 and KD29 show intense CD spectra with double minima at 222 and 208-210 nm, indicating the presence of extensive regions of alpha-helix. DD28 and KD25 have spectra which are reduced in intensity with minima around 215 nm, characteristic of a beta-sheet. The observed spectra are compatible with sequence analysis which predicts that HBD contains alternating stretches of alpha-helix and beta-strand. These extensive decreases in secondary structure in DD28 and KP28 in which the predicted first beta-strand or last alpha-helix was deleted, respectively, were accompanied by the loss of hormone binding activity. On the basis of these results, we suggest a new model for h-TR beta 1 consisting of the known DNA binding domain linked by an alpha-helical hinge to the HBD, with the tertiary structure of an alpha/beta barrel. The model is compatible with previous chemical and genetic studies on the structure of this protein. PMID:8338844

McPhie, P; Parkison, C; Lee, B K; Cheng, S Y

1993-07-27

361

Evidence that. beta. -amyloid protein in Alzheimer's disease is not derived by normal processing  

SciTech Connect

The {beta}-amyloid protein ({beta}/A4), derived from a larger amyloid precursor protein (APP), is the principal component of senile plaques in Alzheimer's disease. APP is an integral membrane glycoprotein and is secreted as a carboxyl-terminal truncated molecule. APP cleavage, which is a membrane-associated event, occurred at a site located within the {beta}/A4 region. This suggests that an intact amyloidogenic {beta}/A4 fragment is not generated during normal APP catabolism. Therefore, an early event in amyloid formation may involve altered APP processing that results in the release and subsequent deposition of intact {beta}/A4.

Sisodia, S.S.; Koo, E.H.; Price, D.L. (Johns Hopkins Univ. School of Medicine, Baltimore, MD (USA)); Beyreuther, K. (Univ. of Heidelberg (West Germany)); Unterbeck, A. (Molecular Therapeutics, West Haven, CT (USA))

1990-04-27

362

Urban Institute:Fact Sheets  

NSDL National Science Digital Library

The Urban Institute produces dozens of timely policy papers and fact sheets that are read widely by policy folks, journalists, and those with a passion for major metropolitan areas. This nice nook of their site provides access to well over 100 of their fact sheets. The topics covered here include housing finance, economic insecurity, Social Security, and the labor force. Visitors can browse through a complete list of all the topics on the left-hand side of the page. The site also contains links to relevant full-length policy reports and a mix of other related links from various policy centers within the Institute. Additionally, users can take advantage of the "Press Room" area which contains additional information on each fact sheet and topical area.

363

Subglacial floods beneath ice sheets.  

PubMed

Subglacial floods (jökulhlaups) are well documented as occurring beneath present day glaciers and ice caps. In addition, it is known that massive floods have occurred from ice-dammed lakes proximal to the Laurentide ice sheet during the last ice age, and it has been suggested that at least one such flood below the waning ice sheet was responsible for a dramatic cooling event some 8000 years ago. We propose that drainage of lakes from beneath ice sheets will generally occur in a time-periodic fashion, and that such floods can be of severe magnitude. Such hydraulic eruptions are likely to have caused severe climatic disturbances in the past, and may well do so in the future. PMID:16782609

Evatt, G W; Fowler, A C; Clark, C D; Hulton, N R J

2006-07-15

364

Root-growth-inhibiting sheet  

DOEpatents

In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a "geotextile" and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

Burton, Frederick G. (Stansbury Park, UT); Cataldo, Dominic A. (Kennewick, WA); Cline, John F. (Prosser, WA); Skiens, W. Eugene (Wilsonville, OR); Van Voris, Peter (Richland, WA)

1993-01-01

365

Optimal swimming of a sheet  

NASA Astrophysics Data System (ADS)

Propulsion at microscopic scales is often achieved through propagating traveling waves along hairlike organelles called flagella. Taylor's two-dimensional swimming sheet model is frequently used to provide insight into problems of flagellar propulsion. We derive numerically the large-amplitude wave form of the two-dimensional swimming sheet that yields optimum hydrodynamic efficiency: the ratio of the squared swimming speed to the rate-of-working of the sheet against the fluid. Using the boundary element method, we show that the optimal wave form is a front-back symmetric regularized cusp that is 25% more efficient than the optimal sine wave. This optimal two-dimensional shape is smooth, qualitatively different from the kinked form of Lighthill's optimal three-dimensional flagellum, not predicted by small-amplitude theory, and different from the smooth circular-arc-like shape of active elastic filaments.

Montenegro-Johnson, Thomas D.; Lauga, Eric

2014-06-01

366

Study on the supramolecular multirecognition mechanism of beta-naphthol/beta-cyclodextrin/anionic surfactant in a tolnaftate hydrolysis system.  

PubMed

Based on the fact that tolnaftate degrade to beta-naphthol sodium (RONa) at 5.00 mol/L NaOH solution and RO(-) was protonated to ROH after being acidified and adjusted to the pH 4.50 by acetic acid-sodium acetate buffer solution, we studied and discussed the mechanism of the supramolecular multirecognition interaction among the anionic surfactants sodium lauryl sulfate (SLS), beta-cyclodextrin (beta-CD), and beta-naphthol (ROH) by means of fluorescence spectrum, surface tension of the solution, infrared spectrograms, and (1)HNMR spectroscopy. The apparent formation constant of the ternary inclusion complex was determined to be (5.48 +/- 0.13) x 10(3) L(2)/mol(2). The thermodynamic parameters (DeltaG degrees, DeltaH degrees, DeltaS degrees ) for the formation of the inclusion complexes were obtained from the van't Hoff equation. It was indicated that the multiple and synergistic protection effect of SLS and beta-CD on the excited singlet state ROH played very important roles in the enhancement of the fluorescence of ROH. Results showed that, at room temperature, the naphthalene ring of ROH and the hydrophobic hydrocarbon chain of SLS were included into the cavity of beta-CD to form a ROH/SLS/beta-CD ternary inclusion complex with stoichiometry of 1:1:1, which provided effective protection for the excited state of ROH and increased the fluorescent intensity of ROH obviously. PMID:16640448

Bo, Tang; Xu, Wang; Jing, Wang; Chengguang, Yu; Zhenzhen, Chen; Yi, Ding

2006-05-01

367

Neutrinoless double beta decay  

E-print Network

The status of the search for neutrinoless double beta decay is reviewed. The effort to reach the sensitivity needed to cover the effective Majorana neutrino mass corresponding to the degenerate and inverted mass hierarchy is described. Various issues concerning the theory (and phenomenology) of the relation between the $0\

Petr Vogel

2006-11-17

368

Drainage through subglacial water sheets  

NASA Astrophysics Data System (ADS)

Subglacial drainage plays an important role in controlling coupling between glacial ice and underlying bed. Here, we study the flow of water in thin, macroporous sheets between ice and bed. Previous work shows that small perturbations in depth of a nearly parallel-sided water film grow unstably because these areas have enhanced viscous dissipation that leads to enhanced melting of an ice roof. We argue that in the presence of bed protrusions bridging a water sheet, downward motion of the ice roof can stabilize this sheet. Stability results when the rate of roof closure increases faster with water depth than the rate of viscous dissipation. We therefore modify existing theory to include protrusions that partially support the overlying glacier. Differences in the pressure on protrusions relative to water pressure drive roof closure. The mechanisms of both regelation and creep normal to the bed close the overlying ice roof and decrease the ice-bed gap. In order to account for multiple protrusion sizes along the bed (for instance, resulting from an assortment of various-sized sediment grains), we incorporate a method of partitioning overburden pressure among different protrusion size classes and the water sheet. Partitioning is dependent on the amount of ice protrusion contact and, therefore, water depth. This method allows prediction of roof closure rates. We then investigate stable, steady sheet configurations for reasonable parameter choices and find that these steady states can occur for modest water depths at very low effective pressures, as is appropriate for ice streams. Moreover, we find that multiple steady sheet thicknesses exist, raising the possibility of switches between low and high hydraulic conductivity regimes for the subglacial water system.

Creyts, Timothy T.; Schoof, Christian G.

2009-10-01

369

Consequences of beta-glucocerebrosidase deficiency in epidermis. Ultrastructure and permeability barrier alterations in Gaucher disease.  

PubMed Central

Hydrolysis of glucosylceramide by beta-glucocerebrosidase results in ceramide, a critical component of the intercellular lamellae that mediate the epidermal permeability barrier. A subset of type 2 Gaucher patients displays ichthyosiform skin abnormalities, as do transgenic Gaucher mice homozygous for a null allele. To investigate the relationship between glucocerebrosidase deficiency and epidermal permeability barrier function, we compared the stratum corneum (SC) ultrastructure, lipid content, and barrier function of Gaucher mice to carrier and normal mice, and to hairless mice treated topically with bromoconduritol B epoxide (BrCBE), an irreversible inhibitor of glucocerebrosidase. Both Gaucher mice and BrCBE-treated mice revealed abnormal, incompletely processed, lamellar body-derived sheets throughout the SC interstices, while transgenic carrier mice displayed normal bilayers. The SC of a severely affected type 2 Gaucher's disease infant revealed similarly abnormal ultrastructure. Furthermore, the Gaucher mice demonstrated markedly elevated transepidermal water loss (4.2 +/- 0.6 vs < 0.10 g/m2 per h). The electron-dense tracer, colloidal lanthanum, percolated between the incompletely processed lamellar body-derived sheets in the SC interstices of Gaucher mice only, demonstrating altered permeability barrier function. Gaucher and BrCBE-treated mice showed < 1% and < 5% of normal epidermal glucocerebrosidase activity, respectively, and the epidermis/SC of Gaucher mice demonstrated elevated glucosylceramide (5- to 10-fold), with diminished ceramide content. Thus, the skin changes observed in Gaucher mice and infants may result from the formation of incompetent intercellular lamellar bilayers due to a decreased hydrolysis of glucosylceramide to ceramide. Glucocerebrosidase therefore appears necessary for the generation of membranes of sufficient functional competence for epidermal barrier function. Images PMID:8163674

Holleran, W M; Ginns, E I; Menon, G K; Grundmann, J U; Fartasch, M; McKinney, C E; Elias, P M; Sidransky, E

1994-01-01

370

Genetics Home Reference: Beta thalassemia  

MedlinePLUS

... cells (anemia), which can cause pale skin, weakness, fatigue, and more serious complications. People with beta thalassemia are at an increased risk of developing abnormal blood clots. Beta thalassemia is ...

371

Sheet Beam Klystron Instability Analysis  

SciTech Connect

Using the principle of energy balance we develop a 2D theory for calculating growth rates of instability in a two-cavity model of a sheet beam klystron. An important ingredient is a TE-like mode in the gap that also gives a longitudinal kick to the beam. When compared with a self-consistent particle-in-cell calculation, with sheet beam klystron-type parameters, agreement is quite good up to half the design current, 65 A; at full current, however, other, current-dependent effects come in and the results deviate significantly.

Bane, K.L.F.; Jensen, A.; Li, Z.; Stupakov, G.; Adolphsen, C.; /SLAC

2009-05-08

372

Biaxially corrugated flexible sheet material  

SciTech Connect

A flexible biaxially corrugated sheet material is formed from a plurality of identical trapezium segments which are arranged in a plurality of long strips a single segment wide. Adjacent strips are mirror images of each other and connected along adjoining sides with the angles of the four corners of adjacent segments being alternately less than 360.degree. and greater than 360.degree. along the length of a strip such that the sheet material has an undulating configuration, and is inherently curved and cannot lie in a flat plane.

Schmertz, John C. (5308 Ellsworth Ave., Pittsburgh, PA 15232)

1991-04-16

373

Quantification of ridging in ferritic stainless steel sheets by electron backscattered diffraction R-value maps.  

PubMed

In ferritic stainless steel (FSS), undesirable surface defects of ridging appear during deep drawing. The formation of these defects is attributed to the inhomogeneous distribution of orientations of individual grains. In the present work, a new electron backscattered diffraction R(?)-value map was introduced, and the dependence of the tensile directions on the formation of ridging in an FSS sheet was discussed using this map. The results showed that large grain colonies in the R(?)-value maps lead to the formation of severe ridging in an FSS sheet. PMID:23920166

Lee, Kye-Man; Park, Jieon; Kim, Sangseok; Park, Sooho; Huh, Moo-Young

2013-08-01

374

A transforming growth factor beta 2 (TGF-beta 2)-like immunosuppressive factor in amniotic fluid and localization of TGF-beta 2 mRNA in the pregnant uterus  

PubMed Central

This report describes a murine amniotic fluid (MAF) immunosuppressive factor that has properties similar to transforming growth factor beta (TGF-beta). The MAF factor exhibits TGF-beta-like activity in stimulating soft agar colony formation by AKR-2B cells and inhibiting thymidine uptake by Mv1Lu cells. We demonstrate that both the immunosuppressive and TGF-beta-like activities of the MAF factor are completely neutralized by anti-TGF-beta 2-specific antibodies and not by anti-TGF-beta 1-specific antisera. The immunosuppressive factor in MAF is novel in that it appears to be identical or very closely related to TGF-beta 2 and is active in its native state. This active and anti- TGF-beta 2-neutralizable factor chromatographs at approximately 70 kD on Sephadex at neutral pH and appears to be able to complex with alpha- fetoprotein in native amniotic fluid. Chromatography of native MAF under acidic conditions demonstrates a lower molecular mass protein that chromatographs on BioGel in the same position as the mature 25-kD TGF-beta. This protein has the biological properties of TGF-beta and is immunosuppressive. Both of these activities are neutralizable with anti- TGF-beta 2 but not with anti-TGF-beta 1 or other antisera. By Northern analysis, we find high levels of TGF-beta 2 mRNA (with little or no TGF- beta 1) in the pregnant uterus that peak around day 15 of gestation and then fall rapidly by day 19 as birth approaches. The TGF-beta 2-like factor could possibly play a role in maternal immunity, in the retention of the fetal allograft, as well as in regulating fetal and neonatal immunological competence. PMID:1700055

1990-01-01

375

Fact Sheet: Summary of Self-Determination. NRC Fact Sheet  

ERIC Educational Resources Information Center

This fact sheet provides an explanation of what self determination is, provides the four principles of self determination, describes the values supported by self determination. The authors contend that if self-determination is going to be successful, it requires that those who supply services and fund them make certain changes in both the way they…

Kennedy, Michael; Lewin, Lori

2010-01-01

376

TURBULENT DYNAMICS IN SOLAR FLARE SHEET STRUCTURES MEASURED WITH LOCAL CORRELATION TRACKING  

SciTech Connect

High-resolution observations of the Sun's corona in extreme ultraviolet and soft X-rays have revealed a new world of complexity in the sheet-like structures connecting coronal mass ejections (CMEs) to the post-eruption flare arcades. This article presents initial findings from an exploration of dynamic flows in two flares observed with Hinode/XRT and SDO/AIA. The flows are observed in the hot ({approx}> 10 MK) plasma above the post-eruption arcades and measured with local correlation tracking. The observations demonstrate significant shears in velocity, giving the appearance of vortices and stagnations. Plasma diagnostics indicate that the plasma {beta} exceeds unity in at least one of the studied events, suggesting that the coronal magnetic fields may be significantly affected by the turbulent flows. Although reconnection models of eruptive flares tend to predict a macroscopic current sheet in the region between the CME and the flare arcade, it is not yet clear whether the observed sheet-like structures are identifiable as the current sheets or 'thermal halos' surrounding the current sheets. Regardless, the relationship between the turbulent motions and the embedded magnetic field is likely to be complicated, involving dynamic fluid processes that produce small length scales in the current sheet. Such processes may be crucial for triggering, accelerating, and/or prolonging reconnection in the corona.

McKenzie, D. E., E-mail: mckenzie@physics.montana.edu [Department of Physics, Montana State University, P.O. Box 173840, Bozeman, MT 59717-3840 (United States)

2013-03-20

377

ON PLASMA KINETIC MODEL OF A 3D SOLAR CORONA AND SOLAR WIND AT HELIOSPHERIC SHEET  

Microsoft Academic Search

The dynamical solar corona in 3D consists of transient type magnetic island elements and radial type magnetic flux rope structures in a heliospheric sheet. During the formation and relaxation these elements produce inductive elec- tromagnetic fields where energetic particles are produced. We study the 3D corona formation in the kinetic approach and parameterize it like a hot current-carrying collisionless plasma

V. M. GUBCHENKO; M. L. KHODACHENKO; H. K. BIERNAT

378

Toward a unified dynamic model for dykes and cone sheets in volcanic systems  

NASA Astrophysics Data System (ADS)

Igneous sheet intrusions, such as dykes and cone sheets, represent various geometries of magma channels through the crust. In many volcanoes, they coexist as parts of complex plumbing systems and are likely fed by common sources. How they form is fundamental regarding volcanic hazards, but yet no dynamic model simulates and predicts satisfactorily the diversity of sheet intrusions observed in volcanic systems. Here we present scaled laboratory experiments that reproduced dyke and cone sheet intrusion geometries under controlled conditions. Combined to a parametric study, a dimensional analysis shows that two dimensionless numbers ?1 and ?2 govern the formation of these intrusions. ?1 is geometrical and describes the geometry of the magma source; ?2 is dynamical and compares the local viscous stresses in the flowing magma to the host-rock strength. Plotting our experiments against these two numbers results in a phase diagram evidencing a dyke and a cone-sheet field, separated by a sharp transition that fits a power law. This result shows that dykes and cone sheets correspond to two distinct physical regimes of magma emplacement in the Earth's crust. Cone sheets preferentially form when their source is shallow relative to their size, when the magma influx (or viscosity) is large, or when the host rock is weak. In addition, both dykes and cone sheets may form from the same source, the shift from one regime to the other being then controlled by magma dynamics, i.e. different values of ?2. We compare our phase diagram to geological data and show that the extrapolated empirical dyke-to-cone sheet transition predicts the occurrence of dykes and cone sheets in various natural volcanic settings. This study thus provides a unified dynamic model of sheet intrusions emplacement and captures fundamental mechanisms of magma transport in the Earth's crust.

Galland, Olivier; Burchardt, Steffi; Hallot, Erwan; Mourgues, Régis; Bulois, Cédric

2014-05-01

379

Vertical Sheet Array of Carbon Nanotubes Grown on Sapphire Substrates Using Atomic Step Distribution  

NASA Astrophysics Data System (ADS)

A vertically standing sheet array composed of carbon nanotubes was successfully fabricated in a self-assembled fashion using the atomic step array on a sapphire surface as a template. The sheet is approximately 1 µm thick, 60 µm high, and as deep as the substrate width. The spacing is approximately 1 µm, which is dependent on the miscut angle of the surface. The sheet-like vertical carbon nanotube growth is caused by preferential formation of cobalt nanoparticles at the atomic steps, which have a highly irregular distribution with a width of ca. 0.5 µm on the as-polished wafer surface.

Yamada, Kazuki; Chokan, Tomohito; Chiashi, Shohei; Homma, Yoshikazu

2010-06-01

380

Expression of S100 beta in sensory and secretory cells of the vertebrate inner ear  

NASA Technical Reports Server (NTRS)

We evaluated anti-S100 beta expression in the chick (Gallus domesticus) inner ear and determined that: 1) the monomer anti-S100 beta is expressed differentially in the vestibular and auditory perikarya; 2) expression of S100 beta in the afferent nerve terminals is time-related to synapse and myelin formation; 3) the expression of the dimer anti-S100 alpha alpha beta beta and monomer anti-S100 beta overlaps in most inner ear cell types. Most S100 alpha alpha beta beta positive cells express S100 beta, but S100 beta positive cells do not always express S100 alpha alpha beta beta. 4) the expression of S100 beta is diffused over the perikaryal cytoplasm and nuclei of the acoustic ganglia but is concentrated over the nuclei of the vestibular perikarya. 6) S100 beta is expressed in secretory cells, and it is co-localized with GABA in sensory cells. 7) Color thresholding objective quantitation indicates that the amount of S100 beta was higher (mean 22, SD +/- 4) at E19 than at E9 (mean 34, SD +/- 3) in afferent axons. 8) Moreover, S100 beta was unchanged between E11-E19 in the perikaryal cytoplasm, but did change over the nuclei. At E9, 74%, and at E21, 5% of vestibular perikarya were positive. The data suggest that S100 beta may be physically associated with neuronal and ionic controlling cells of the vertebrate inner ear, where it could provide a dual ionic and neurotrophic modulatory function.

Fermin, C. D.; Martin, D. S.

1995-01-01

381

THE FREE-FALL TIME OF FINITE SHEETS AND FILAMENTS  

SciTech Connect

Molecular clouds often exhibit filamentary or sheet-like shapes. We compute the free-fall time ({tau}{sub ff}) for finite, uniform, self-gravitating circular sheets and filamentary clouds of small but finite thickness, so that their volume density {rho} can still be defined. We find that, for thin sheets, the free-fall time is larger than that of a uniform sphere with the same volume density by a factor proportional to {radical}A, where the aspect ratio A is given by A = R/h, R being the sheet's radius and h is its thickness. For filamentary clouds, the aspect ratio is defined as A=L/R, where L is the filament's half-length and R is its (small) radius, and the modification factor is more complicated, although in the limit of large A it again reduces to nearly {radical}A. We propose that our result for filamentary shapes naturally explains the ubiquitous configuration of clumps fed by filaments observed in the densest structures of molecular clouds. Also, the longer free-fall times for non-spherical geometries in general may contribute toward partially alleviating the 'star formation conundrum', namely, the star formation rate in the Galaxy appears to be proceeding in a timescale much larger than the total molecular mass in the Galaxy divided by its typical free-fall time. If molecular clouds are in general formed by thin sheets and long filaments, then their relevant free-fall time may have been systematically underestimated, possibly by factors of up to one order of magnitude.

Toala, Jesus A. [Currently at Instituto de Astrofisica de Andalucia, CSIC, E-1808, Granada (Spain); Vazquez-Semadeni, Enrique; Gomez, Gilberto C. [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Campus Morelia Apartado Postal 3-72, 58090 Morelia, Michoacan (Mexico)

2012-01-10

382

Structure and Dynamics of Current Sheets in 3D Magnetic Fields with the X-line  

Microsoft Academic Search

Experimental results are presented on the structure of current sheets formed in 3D magnetic fields with singular lines of the X-type. Two basic diagnostics were used with the device CS - 3D: two-exposure holographic interferometry and magnetic measurements. Formation of extended current sheets and plasma compression were observed in the presence of the longitudinal magnetic field component aligned with the

Anna G. Frank; S. Yu. Bogdanov; S. G. Bugrov; V. S. Markov; G. V. Dreiden; G. V. Ostrovskaya

2004-01-01

383

21 CFR 878.4025 - Silicone sheeting.  

Code of Federal Regulations, 2012 CFR

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4025 Silicone sheeting. (a) Identification . Silicone sheeting...

2012-04-01

384

21 CFR 878.4025 - Silicone sheeting.  

Code of Federal Regulations, 2013 CFR

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4025 Silicone sheeting. (a) Identification . Silicone sheeting...

2013-04-01

385

21 CFR 878.4025 - Silicone sheeting.  

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4025 Silicone sheeting. (a) Identification. Silicone sheeting...

2014-04-01

386

21 CFR 878.4025 - Silicone sheeting.  

Code of Federal Regulations, 2011 CFR

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4025 Silicone sheeting. (a) Identification . Silicone sheeting...

2011-04-01

387

Cell sheet technology for cardiac tissue engineering.  

PubMed

In this chapter, we describe the methods for the fabrication and transfer/transplantation of 3D tissues by using cell sheet technology for cardiac tissue regeneration. A temperature-responsive culture surface can be fabricated by grafting a temperature-responsive polymer, poly(N-isopropylacrylamide), onto a polystyrene cell culture surface. Cells cultured confluently on such a culture surface can be recovered as an intact cell sheet, and functional three-dimensional (3D) tissues can then be easily fabricated by layering the recovered cell sheets without any scaffolds or complicated manipulation. Cardiac cell sheets, myoblast sheets, mesenchymal stem cell sheets, cardiac progenitor cell sheets, etc., which are prepared from temperature-responsive culture surfaces, can be easily transplanted onto heart tissues of animal models, and those cell sheet constructs enhance the cell transplant efficiency, resulting in the induction of effective therapy. PMID:25070334

Haraguchi, Yuji; Shimizu, Tatsuya; Matsuura, Katsuhisa; Sekine, Hidekazu; Tanaka, Nobuyuki; Tadakuma, Kenjiro; Yamato, Masayuki; Kaneko, Makoto; Okano, Teruo

2014-01-01

388

Photovoltaic Reliability and Engineering (Revised) (Fact Sheet)  

SciTech Connect

Capabilities fact sheet for the National Center for Photovoltaics: Photovoltaic Reliability and Engineering. One-sided sheet that includes Scope, Core Competencies and Capabilities, and Contact/Web information.

Not Available

2011-06-01

389

Fabrication of Niobium sheet for RF cavities  

E-print Network

angular extrusion (ECAE) and then cross rolling to obtain sheets. This work is a study of the effect different thermomechanical processing variables have on the microstructure niobium sheets. Recrystallization behaviors strongly depended on the purity...

Balachandran, Shreyas

2009-05-15

390

Guidance Document Material Safety Data Sheet  

E-print Network

Guidance Document Material Safety Data Sheet A Material Safety Data Sheet (MSDS) provides you for assistance. Many MSDSs are up on the Internet. Use any search engine to find sites or click here: http

391

Structure, dynamics, and stability of beta-cyclodextrin inclusion complexes of aspartame and neotame.  

PubMed

Studies of the high-intensity sweetener aspartame show that its stability is significantly enhanced in the presence of beta-cyclodextrin (beta-CyD). At a 5:1 beta-CyD/aspartame molar ratio, the stability of aspartame is 42% greater in 4 mM phosphate buffer (pH 3.1) compared to solutions prepared without beta-CyD. Solution-state (1)H NMR experiments demonstrate the formation of 1:1 beta-CyD/aspartame complexes, stabilized by the interaction of the phenyl-ring protons of aspartame with the H3 and H5 protons of beta-CyD. Inclusion complex formation clearly accounts for the observed stability enhancement of aspartame in solution. The formation of inclusion complexes in solution is also demonstrated for beta-CyD and neotame, a structural derivative of aspartame containing an N-substituted 3,3-dimethylbutyl group. These complexes are stabilized by the interaction of beta-CyD with both phenyl-ring and dimethylbutyl protons. Solid-state NMR experiments provide additional characterization, clearly demonstrating the formation of inclusion complexes in lyophilized solids prepared from solutions of beta-CyD and either aspartame or neotame. PMID:11308366

Garbow, J R; Likos, J J; Schroeder, S A

2001-04-01

392

IMMUNIZATION COVER SHEET HEALTH SERVICES  

E-print Network

Please keep a copy of all documents submitted for your personal records For more information, pleaseIMMUNIZATION COVER SHEET HEALTH SERVICES 327 HIGH STREET MIDDLETOWN, CT 06459 University Health Services Use GLSP Office Use Student meets all requirements ­ initials and date: Student record updated

Royer, Dana

393

Profile of Accreditation. Fact Sheet.  

ERIC Educational Resources Information Center

This fact sheet presents information about the accreditation of institutions of higher education in the United States. Accreditation is a process of external quality review used to scrutinize colleges, universities, and educational programs for quality assurance and improvement. In the United States, in 2002, 6,421 institutions were accredited,…

Council for Higher Education Accreditation, Washington, DC.

394

Finance Degree Curriculum Information Sheet  

E-print Network

Finance Degree Curriculum Information Sheet 33:010:275-Intro. to Managerial Accounting (3) (pre-req: 33:010:272) 33:011:300-Business Forum (2) 33:390:310-Financial Management for Finance Majors (3)* 33:390:400-Corporate Finance (3) (pre-req: 33:390:310) 4 Finance electives (12) * Beginning Fall 2013

Lin, Xiaodong

395

Media Tips Sheet Summer 2010  

E-print Network

Media Tips Sheet Summer 2010 Find Story Ideas in Our Monthly Online News Magazine: http · Descriptions of vision-related images · Answers to eye health questions Sign up for the RSS feed and e children, and how researchers have discovered a treatment that holds so much hope. Visit Our Online Press

Bandettini, Peter A.

396

Project Fact Sheet Project Brief  

E-print Network

Project Fact Sheet Project Brief: In the first phase of the Union Building re-development to the Concert Hall and a new mezzanine on the second floor will provide ad- ditional storage space to the Union that it adapts to meet the needs of a changing student body. The re-development plans are grounded in a full

397

Product Sheet Wall Mount Lift  

E-print Network

Product Sheet Wall Mount Lift Ergotron® Neo-FlexTM 870-05-061, rev. 12/11/07 www-Flex Wall Mount Lift! CF patented lift-and-pivot motion technology adjusts with a light touch. Raise-Flex Wall Mount Lift Commercial Part Number: 60-577-195 (black) Options: Works with a variety of Ergotron

Saskatchewan, University of

398

JOB EVALUATION QUESTIONNAIRE ANSWER SHEET  

E-print Network

JOB EVALUATION QUESTIONNAIRE ANSWER SHEET DO NOT WRITE IN THIS SPACE N.C. Date Received Reclass New Starting Date in Class Yes No NA (NA if Temporary Job) Notice # Effective Date If Reclassified IS TO BE USED WITH THE JOB EVALUATION QUESTIONNAIRE (BA 802) ONLY FOR POSITIONS COVERED BY CIVIL SERVICE

Amin, S. Massoud

399

RESISTANCE SPOT WELDING BERYLLIUM SHEET  

Microsoft Academic Search

It was determined that beryllium cross-rolled sheet can be resistance ; welded. Pre- and post-heating reduced the tendency for cracking by reducing the ; residual stress level during cooling. The cast nugget grain size was dependent ; on base metal grain size. Electrode sticking was reduced by improved surface ; finish. Beryllium weldments showed adequate strength only if proper design

Jahnle

1962-01-01

400

FACT SHEETS HIV and Pregnancy  

E-print Network

. In areas with opt-out testing, HIV testing is automatically included as part of rou tine prenatal careFACT SHEETS HIV and Pregnancy HIV Testing and Pregnancy Mother-to-Child Transmission of HIV Anti in managing HIV dur ing pregnancy. Table of Contents 1. HIV Testing and Pregnancy 2. Mother

Levin, Judith G.

401

Account Information Sheet December 2010  

E-print Network

User Guide to the Account Information Sheet (AIS) December 2010 #12;Proposal Tracking AIS ­ User AIS, please contact AISprob@upenn.edu #12;Proposal Tracking AIS ­ User Guide University ------------------------------------------------------------------------------------------------------------------- #12;Proposal Tracking AIS ­ User Guide University of Pennsylvania Page 4 of 14 Account Information

Bushman, Frederic

402

Magnetic Resonance Facility (Fact Sheet)  

SciTech Connect

This fact sheet provides information about Magnetic Resonance Facility capabilities and applications at NREL's National Bioenergy Center. Liquid and solid-state analysis capability for a variety of biomass, photovoltaic, and materials characterization applications across NREL. NREL scientists analyze solid and liquid samples on three nuclear magnetic resonance (NMR) spectrometers as well as an electron paramagnetic resonance (EPR) spectrometer.

Not Available

2012-03-01

403

Changes in the Antarctic Ice Sheet  

NSDL National Science Digital Library

The Antarctic ice sheet changes in size over the course of a year. When it is summer in the southern hemisphere, the ice sheet decreases in size. As the ice sheet melts, it releases fresh water into the ocean. In the southern winter (our summer), the ice refreezes, drawing fresh water out of the surrounding ocean, leaving the salt behind. These seasonal changes in the ice sheet are examined in this activity, utilizing satellite imagery.

2000-05-31

404

Epistemology of Ice Sheet Change  

NASA Astrophysics Data System (ADS)

Recent change in the Greenland and West Antarctic ice sheets is observed as surface lowering accompanied by speed up of the ice. One of two types of perturbation is usually invoked to account for these changes, unbalanced forces at either the bed or at the marine margin of the ice sheet. The former is linked to change in meltwater at the bed while the latter is linked to a change in the temperature of the ocean near the margin. Observational data have been used together with numerical models to reproduce both cases. What we ask here is whether or not there is anything distinctive in the observed patterns of change that warrants preferring one type of perturbation over the other. That is, our interest is epistemological: is there anything distinctive in the pattern of ice sheet response to environmental forcing that allows the correct forcing to be identified using observational data? We hypothesize that specific changes in ice dynamics—perturbation at the bed or at the margin—lead to unique patterns of change in ice sheet flow, and thus geometry. For example, ocean warming may have its largest expression close to the coast and then propagate into the interior on time and spatial scales set by the material properties of the ice and various boundary conditions. Other perturbations may yield different patterns. The hypothesis is tested using an ice sheet model and a set of simple perturbations that represent environmental changes that might drive ice sheet change. We use surface lowering (ice thinning) as our indicator of change and conduct an EOF analysis to identify modes in that time dependent field. If leading modes derived from different perturbation experiments are distinguishable, the null hypothesis—that there is nothing diagnostic in the observed changes—is rejected and we conclude that observed patterns of change in ice sheets may be used to identify underlying causes for that change. This, in turn, would yield normal mode "finger prints" for different types of perturbations that could be used to interpret observed patterns of change.

Waibel, M. S.; Hulbe, C. L.; Johnson, J. V.

2012-12-01

405

Salmon, Mississippi Fact Sheet  

SciTech Connect

The Salmon, Mississippi, Site, also called the Tatum Dome Test Site, is a 1,470-acre tract of land in Lamar County, Mississippi, 21 miles southwest of Hattiesburg. The nearest town is Purvis, about 10 miles east of the site. The site is in a forested region known as the long-leaf pine belt of the Gulf Coastal Plain. Elevations in the area range from about 240 to 350 feet above sea level. The site overlies a salt formation called the Tatum Salt Dome. Land around the Salmon site has residential, industrial, and commercial use, although no one lives within the boundary of the site itself. The U.S. Atomic Energy Commission, a predecessor agency of the U.S. Department of Energy (DOE), and the U.S. Department of Defense conducted two underground nuclear tests at the site under the designation of Project Dribble, part of a larger program known as the Vela Uniform program. Two gas explosive tests, designated Project Miracle Play, were also conducted at the site.

None

2010-01-04

406

Structure-based design of non-natural amino-acid inhibitors of amyloid fibril formation  

SciTech Connect

Many globular and natively disordered proteins can convert into amyloid fibrils. These fibrils are associated with numerous pathologies as well as with normal cellular functions, and frequently form during protein denaturation. Inhibitors of pathological amyloid fibril formation could be useful in the development of therapeutics, provided that the inhibitors were specific enough to avoid interfering with normal processes. Here we show that computer-aided, structure-based design can yield highly specific peptide inhibitors of amyloid formation. Using known atomic structures of segments of amyloid fibrils as templates, we have designed and characterized an all-D-amino-acid inhibitor of the fibril formation of the tau protein associated with Alzheimer's disease, and a non-natural L-amino-acid inhibitor of an amyloid fibril that enhances sexual transmission of human immunodeficiency virus. Our results indicate that peptides from structure-based designs can disrupt the fibril formation of full-length proteins, including those, such as tau protein, that lack fully ordered native structures. Because the inhibiting peptides have been designed on structures of dual-{beta}-sheet 'steric zippers', the successful inhibition of amyloid fibril formation strengthens the hypothesis that amyloid spines contain steric zippers.

Sievers, Stuart A.; Karanicolas, John; Chang, Howard W.; Zhao, Anni; Jiang, Lin; Zirafi, Onofrio; Stevens, Jason T.; Münch, Jan; Baker, David; Eisenberg, David (UCLA); (UWASH); (UL); (Kansas); (Ulm)

2011-09-20

407

Type beta Transforming Growth Factor is the Primary Differentiation-Inducing Serum Factor for Normal Human Bronchial Epithelial Cells  

Microsoft Academic Search

Type beta transforming growth factor (TGF-beta ) was shown to be the serum factor responsible for inducing normal human bronchial epithelial (NHBE) cells to undergo squamous differentiation. NHBE cells were shown to have high-affinity receptors for TGF-beta . TGF-beta induced the following markers of terminal squamous differentiation in NHBE cells: (i) increase in Ca ionophore-induced formation of crosslinked envelopes; (ii)

Tohru Masui; Lalage M. Wakefield; John F. Lechner; Moira A. La Veck; Michael B. Sporn; Curtis C. Harris

1986-01-01

408

Intraislet release of interleukin 1 inhibits beta cell function by inducing beta cell expression of inducible nitric oxide synthase  

PubMed Central

Cytokines, released in and around pancreatic islets during insulitis, have been proposed to participate in beta-cell destruction associated with autoimmune diabetes. In this study we have evaluated the hypothesis that local release of the cytokine interleukin 1 (IL-1) by nonendocrine cells of the islet induce the expression of inducible nitric oxide synthase (iNOS) by beta cells which results in the inhibition of beta cell function. Treatment of rat islets with a combination of tumor necrosis factor (TNF) and lipopolysaccharide (LPS), conditions known to activate macrophages, stimulate the expression of iNOS and the formation of nitrite. Although TNF+LPS induce iNOS expression and inhibit insulin secretion by intact islets, this combination does not induce the expression of iNOS by beta or alpha cells purified by fluorescence activated cell sorting (Facs). In contrast, IL-1 beta induces the expression of iNOS and also inhibits insulin secretion by both intact islets a