oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 84 )

2018 ( 190 )

2017 ( 213 )

2016 ( 267 )

Custom range...

Search Results: 1 - 10 of 146994 matches for " F Jon Kull "
All listed articles are free for downloading (OA Articles)
Page 1 /146994
Display every page Item
A kinesin motor in a force-producing conformation
Elisabeth Heuston, C Eric Bronner, F Jon Kull, Sharyn A Endow
BMC Structural Biology , 2010, DOI: 10.1186/1472-6807-10-19
Abstract: Here we show that mutation of a single residue in the kinesin-14 Ncd causes the motor to release ADP and hydrolyze ATP faster than wild type, but move more slowly along microtubules in gliding assays, uncoupling nucleotide hydrolysis from force generation. A crystal structure of the motor shows a large rotation of the stalk, a conformation representing a force-producing stroke of Ncd. Three C-terminal residues of Ncd, visible for the first time, interact with the central β-sheet and dock onto the motor core, forming a structure resembling the kinesin-1 neck linker, which has been proposed to be the primary force-generating mechanical element of kinesin-1.Force generation by minus-end Ncd involves docking of the C-terminus, which forms a structure resembling the kinesin-1 neck linker. The mechanism by which the plus- and minus-end motors produce force to move to opposite ends of the microtubule appears to involve the same conformational changes, but distinct structural linkers. Unstable ADP binding may destabilize the motor-ADP state, triggering Ncd stalk rotation and C-terminus docking, producing a working stroke of the motor.Motor proteins of the kinesin family hydrolyze ATP and use the energy released by nucleotide hydrolysis to move along microtubules, performing essential roles in transport, division and other cellular processes. The mechanism by which motors produce force to move on microtubules is not fully understood and remains an outstanding problem in the field. A prevailing hypothesis is that the motor undergoes a conformational change that, under load, produces strain. The strain is relieved by a force-producing movement that displaces the motor relative to the microtubule [1]. Coupling of steps of ATP hydrolysis to the force-producing structural changes of the motor is thought to drive motor movement along microtubules.Progress in understanding the motor mechanism has come from the discovery of the kinesin-14 motors. The motors in this kinesin group bin
KOI-2939b: the largest and longest-period Kepler transiting circumbinary planet
Veselin B. Kostov,Jerome A. Orosz,William F. Welsh,Laurance R. Doyle,Daniel C. Fabrycky,Nader Haghighipour,Billy Quarles,Donald R. Short,William D. Cochran,Michael Endl,Eric B. Ford,Joao Gregorio,Tobias C. Hinse,Howard Isaacson,Jon M. Jenkins,Eric L. N. Jensen,Ilya Kull,David W. Latham,Jack J. Lissauer,Geoffrey W. Marcy,Tsevi Mazeh,Tobias W. A. Muller,Joshua Pepper,Samuel N. Quinn,Darin Ragozzine,Avi Shporer,Jason H. Steffen,Guillermo Torres,Gur Windmiller,William J. Borucki
Physics , 2015,
Abstract: We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the still-small family of CBPs defies the current trend of known short-period planets orbiting near the stability limit of binary stars. Unlike the previous discoveries, the planet revolving around the eclipsing binary system KOI-2939 has a very long orbital period (~1100 days) and was at conjunction only twice during the Kepler mission lifetime. Due to the singular configuration of the system, KOI-2939b is not only the longest-period transiting CBP at the time of writing, but also one of the longest-period transiting planets. With a radius of 1.06+/-0.01 RJup it is also the largest CBP to date. The planet produced three transits in the light-curve of KOI-2939 (one of them during an eclipse, creating a syzygy) and measurably perturbed the times of the stellar eclipses, allowing us to measure its mass to be 1.52+/-0.65 MJup. The planet revolves around an 11-day period eclipsing binary consisting of two Solar-mass stars on a slightly inclined, mildly eccentric (e_bin = 0.16), spin-synchronized orbit. Despite having an orbital period three times longer than Earth's, KOI-2939b is in the conservative habitable zone of the binary star throughout its orbit.
Air photo evidence of historical land cover change in the highlands: Wetlands and grasslands give way to crops and woodlots
CA Kull
Madagascar Conservation & Development , 2012,
Abstract: Madagascar’s high plateau – where people farm, graze cattle, and set periodic fire in a grass dominated landscape – receives disproportionately little conservation attention. An aerial photograph-based analysis of land - cover change in the latter half of the 20th century, based on a stratified random sample of twenty eight sites, reveals dramatic trends associated with an increasing human population that is building a cultural landscape of villages and agro-ecosystems to assure its livelihoods. On average across the sample sites, about 23 % of grassland areas present in 1949–1950 were converted to crops fields, farm trees and built - up areas by the 1990s. Of all land - cover transitions, the most dramatic changes included the loss of approximately 60 % of wetlands and 37 % of riparian forests. These land covers, which are dispersed along the fine - grained dendritic stream network, are habitat for crayfish, frogs, and other fauna, yet are also prized locations in the rice - based Malagasy agricultural system. The results of this study suggest that attention be given to highland grassland, wetland and riparian forest ecosystem restoration and conservation; however, any on - the - ground initiatives should incorporate respect for local needs and allow sustainable use of these ecosystems, given their cultural and subsistence importance.
Physical activity and mental health: relationships between depressiveness, psychological disorders and physical activity level in women
M Kull
Biology of Sport , 2003,
Abstract: This research was conducted with an objective to study relationships between physical activity and emotional wellbeing of women. The study involved 659 women aged 18–45. The following questionnaires were used: General Health Questionnaire, Health Questionnaire for Adults, Beck Depression Inventory. Physically active women experienced less stress disorders (P<0.05) and less depressiveness (P<0.05). Results showed that even a low level of physical activity (1-2 times per week) can account for positive impact on women’s mental health (depressive feelings and psychological disorders).
Quantum Mechanical Motion of Relativistic Particle in Non-Continuous Spacetime
A. Kull
Physics , 2002, DOI: 10.1016/S0375-9601(02)01238-0
Abstract: The quantum mechanical motion of a relativistic particle in a non-continuous spacetime is investigated. The spacetime model is a dense, rationale subset of two-dimensional Minkowski spacetime. Solutions of the Dirac equation are calculated using a generalized version of Feynman's checkerboard model. They turn out to be closely related to the continuum propagator.
A Model for the Density Distribution of Virialized CDM Halos
A. Kull
Physics , 1999, DOI: 10.1086/311990
Abstract: An analytic collapse model for the formation and density distribution of virialized cold dark matter halos is proposed. Hierarchical structure formation is taken into account explicitly. Monte Carlo methods are used to generate samples of mass histories of virialized halos. The mean density distribution found from the collapse model is in good agreement with numerical results in the mass range from $10^{11}M_\odot$ to $10^{15}M_\odot$ and in the radial range form $0.05 r_{200}$ to $r_{200}$.
Genomic Imprinting of Grb10?: Coadaptation or Conflict?
Jon F. Wilkins
PLOS Biology , 2014, DOI: 10.1371/journal.pbio.1001800
Abstract: Mammalian development involves significant interactions between offspring and mother. But is this interaction a carefully coordinated effort by two individuals with a common goal—offspring survival? Or is it an evolutionary battleground (a central idea in our understanding of reproduction). The conflict between parents and offspring extends to an offspring's genes, where paternally inherited genes favor demanding more from the mother, while maternally inherited genes favor restraint. This “intragenomic conflict” (among genes within a genome) is the dominant evolutionary explanation for “genomic imprinting.” But a new study in PLOS Biology provides support for a different perspective: that imprinting might facilitate coordination between mother and offspring. According to this “coadaptation theory,” paternally inherited genes might be inactivated because maternally inherited genes are adapted to function harmoniously with the mother. As discussed in this article, the growth effects associated with the imprinted gene Grb10 are consistent with this idea, but it remains to be seen just how general the pattern is.
Fast approximate hierarchical clustering using similarity heuristics
Meelis Kull, Jaak Vilo
BioData Mining , 2008, DOI: 10.1186/1756-0381-1-9
Abstract: We propose an approximate AHC algorithm HappieClust which can output a biologically meaningful clustering of a large dataset more than an order of magnitude faster than full AHC algorithms. The key to the algorithm is to limit the number of calculated pairwise distances to a carefully chosen subset of all possible distances. We choose distances using a similarity heuristic based on a small set of pivot objects. The heuristic efficiently finds pairs of similar objects and these help to mimic the greedy choices of full AHC. Quality of approximate AHC as compared to full AHC is studied with three measures. The first measure evaluates the global quality of the achieved clustering, while the second compares biological relevance using enrichment of biological functions in every subtree of the clusterings. The third measure studies how well the contents of subtrees are conserved between the clusterings.The HappieClust algorithm is well suited for large-scale gene expression visualization and analysis both on personal computers as well as public online web applications. The software is available from the URL http://www.quretec.com/HappieClust webciteVarious types of biological data resulting from high-throughput experiments require analysis, often consisting of many steps. The first steps tend to be unsupervised and require little or no input from the user, while the further steps need more human-computer interaction. One possible starting point of interaction is showing an overview of the data to the user, frequently achieved using clustering.Partitioning-based clustering methods like K-means split the data into non-overlapping clusters [1]. In this article, we concentrate on hierarchical methods that model the data in a tree structure and thus leave more freedom to the user.Probably the most well-known hierarchical clustering method is agglomerative hierarchical clustering (AHC). To begin with, AHC treats each data object as a separate cluster. The following agglomeration
Air photo evidence of historical land cover change in the highlands: Wetlands and grasslands give way to crops and woodlots
Christian A. Kull
Madagascar Conservation & Development , 2012,
Abstract: Madagascar’s high plateau – where people farm, graze cattle, and set periodic fire in a grass dominated landscape – receives disproportionately little conservation attention. An aerial photograph-based analysis of land - cover change in the latter half of the 20th century, based on a stratified random sample of twenty eight sites, reveals dramatic trends associated with an increas-ing human population that is building a cultural landscape of villages and agro-ecosystems to assure its livelihoods. On average across the sample sites, about 23 % of grassland areas present in 1949–1950 were converted to crops fields, farm trees and built - up areas by the 1990s. Of all land - cover transitions, the most dramatic changes included the loss of approximately 60 % of wetlands and 37 % of riparian forests. These land covers, which are dispersed along the fine - grained dendritic stream network, are habitat for crayfish, frogs, and other fauna, yet are also prized locations in the rice - based Malagasy agricultural system. The results of this study suggest that attention be given to highland grassland, wetland and riparian forest ecosystem restoration and conservation; however, any on - the - ground initiatives should incorporate respect for local needs and allow sustainable use of these ecosystems, given their cultural and subsistence importance. RéSUMéLes hautes terres malgaches, dominées par une végétation herbacée, sont des paysages fortement marqués par la gestion productive qu’y exerce l’Homme ; qu’il s’agisse des pratiques culturales, de l’élevage ou de la manipulation des régimes du feu. Cette région ne re oit généralement pas d’intérêt pour la conservation de la biodiversité. Cet article présente les résultats d’une étude régionale de changement d’occupation des sols et des dynamiques des formations végétales des hautes terres au cours de la deuxième moitié du XXe siècle. L’étude est basée sur l’analyse de photographies aériennes prises entre 1949–1950 et 1990–1993 de 28 parcelles de 10 km2 sélectionnées dans un échantillon aléatoire et spatialement stratifié. Les résultats confirment plusieurs tendances liées à l’implantation d’une population agricole croissante : 23 pourcent du terrain qui était couvert de formations graminéennes (herbeuses) en 1950 ont été remplacés par des champs pour l’agriculture, des plantations arborées et des zones résidentielles. Mais la catégorie de couverture végétale qui a été transformée le plus fortement est les zones humides (les marécages), dont la superficie a diminué de 60 pourcent. De plus, 37 pourcent de la superficie
Changes in surface wind directions in Estonia during 1966–2008 and their relationships with large-scale atmospheric circulation
Jaak Jaagus,Ain Kull
Estonian Journal of Earth Sciences , 2011, DOI: 10.3176/earth.2011.4.03
Abstract: Changes in the percentages of eight main surface wind directions at 14 meteorological stations in Estonia, Northeast Europe, were studied during 1966–2008. Long-term changes in wind directions are related to variations in the large-scale atmospheric circulation but partly also to changes in the surroundings of the stations and in wind obstacles. Significant alterations in wind directions were determined, and found to be the strongest in the winter season. The percentages of W and SW winds have clear positive trends, while SE, E and NE winds are characterized by negative tendencies in winter. In conclusion, wind directions have probably been shifted from east to west. Differences in trends between the stations are explained by changes in wind obstacles around the stations. The trends in wind roses in Estonia were caused by the intensification of the westerly circulation over the Atlantic/European sector during the winter season.
Page 1 /146994
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.