Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2020 ( 2 )

2019 ( 298 )

2018 ( 335 )

2017 ( 339 )

Custom range...

Search Results: 1 - 10 of 198875 matches for " Katrina N. Lester "
All listed articles are free for downloading (OA Articles)
Page 1 /198875
Display every page Item
Distinct Structural Features of G Protein-Coupled Receptor Kinase 5 (GRK5) Regulate Its Nuclear Localization and DNA-Binding Ability
Laura R. Johnson, James D. Robinson, Katrina N. Lester, Julie A. Pitcher
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062508
Abstract: G protein-coupled receptor kinases (GRKs) act to desensitize G protein-coupled receptors (GPCRs). In addition to this role at the plasma membrane, a nuclear function for GRK5, a member of the GRK4 subfamily of GRKs, has been reported. GRK5 phosphorylates and promotes the nuclear export of the histone deacetylase, HDAC5. Here we demonstrate that the possession of a nuclear localization sequence (NLS) is a common feature of GRK4 subfamily members (GRKs 4, 5 and 6). However, the location of the NLS and the ability of these GRKs to bind DNA in vitro are different. The NLSs of GRK5 and 6 bind DNA in vitro, whilst the NLS of GRK4 does not. Using mutants of GRK5 we identify the regions of GRK5 required for DNA-binding in vitro and nuclear localization in cells. The DNA-binding ability of GRK5 requires both the NLS and an N-terminal calmodulin (CaM)-binding site. A functional nuclear export sequence (NES), required for CaM-dependent nuclear export of the kinase, is also identified. Based on our observations we propose a model to explain how nuclear localization of GRK5 may be regulated. Notably, the nuclear localization of GRK5 and 6 is differentially regulated. These results suggest subfamily specific nuclear functions for the GRK4 subfamily members. Identification of GRK specific small molecule inhibitors of nuclear localization and/or function for the GRK4 subfamily may thus be an achievable goal.
Multi-frequency observations of E-region HF radar aurora
S. E. Milan,M. Lester,N. Sato
Annales Geophysicae (ANGEO) , 2003,
Abstract: Multi-frequency observations of E-region coherent backscatter from decametre waves reveal that auroral echoes tend to comprise two spectral components superimposed, one at low Doppler shifts, below 250 ms-1, and the other Doppler shifted to near the ion-acoustic speed or above, up to 800 ms-1. The low Doppler shift component occurs at all look directions; Doppler shifts near the ion acoustic speed occur when looking at low flow angles along the direction of the electron drift in the electrojet, and Doppler shifts in excess of the ion acoustic speed occur at intermediate flow angles. The latter population appears most commonly at radar frequencies near 10–12 MHz, with its occurrence decreasing dramatically at higher frequencies. The velocity of the high Doppler shift echoes increases with increasing radar frequency, or irregularity wave number k. The velocity of the low Doppler shift population appears to be suppressed significantly below the line-of-sight component of the electron drift. Initial estimates of the altitude from which scatter occurs suggest that the high Doppler shift echoes originate from higher in the E-region than the low Doppler shift echoes, certainly in the eastward electrojet. We discuss these observations with reference to the theories of de/stabilization of two-stream waves by electron density gradients and electrostatic ion cyclotron waves excited by field-parallel electron drifts. Key words. Ionosphere (ionospheric irregularities)
School Choice of Computing Students: A Comparative Perspective from Two Universities  [PDF]
Rex P. Bringula, Ma. Ymelda C. Batalla, Shirley D. Moraga, Lester Dave R. Ochengco, Kyle N. Ohagan, Rolando R. Lansigan
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.326161
Abstract: This descriptive study utilized a validated questionnaire to determine the profile of two sets of students and their level of consideration in deciding to enroll in their University. It also determined whether their level of consideration in deciding to enroll in their University significantly differed from each other. It was found out that most of the University of the East (UE) and National University (NU) respondents were male respondents taking up Information Technology. They did not have a home province, lived in Manila and Quezon City, lived in family-owned houses, belonged to a family with five family members, and travelled at least an hour in going to school through jeepneys. On the other hand, they were different in terms of family monthly income (most of the UE respondents belonged to a family with a higher family monthly income) and number of family members who studied in the University (most of the NU respondents had at least one member who studied in the same University). It was also noted that more than a quarter of NU respondents lived near their school. UE and NU respondents agreed that they considered nine and five, respectively, of the eleven institutional image indicators in deciding to enroll in the University. UE respondents had the highest consideration on Admission Process and Course Offering while NU respondents had the highest consideration on Scholarships and Grants. Test of difference between means revealed that the level of considerations of the respondents on the institutional image indicators significantly differed in nine out of the eleven indicators. Thus, the null hypothesis stating that there is no significant difference in the level of consideration of the respondents in deciding to enroll in the two Universities in terms of institutional image indicators is partially rejected. Conclusions, recommendations, and limitations of the study were also discussed.
Ultrasound of Primary Aneurysmal Bone Cyst
Katrina N. Glazebrook,Gary L. Keeney,Michael G. Rock
Case Reports in Radiology , 2014, DOI: 10.1155/2014/101069
Abstract: Aneurysmal bone cysts (ABC) are rare, benign, expansile lesions of bone often found in the metaphyses of long bones in pediatric and young adult population. Multiple fluid levels are typically seen on imaging with magnetic resonance imaging (MRI) or computed tomography (CT). We describe a case of a primary ABC in the fibula of a 34-year-old man diagnosed on ultrasound with a mobile fluid level demonstrated sonographically. 1. Introduction Aneurysmal bone cysts (ABC) are rare, benign, expansile lesions of bone most commonly found in the metaphyses of long bones in pediatric and young adult population. The lesion is characterized by blood filled spaces separated by fibrous septa that may contain osteoclast-like giant cells. It can be a primary lesion or arise adjacent to other benign or malignant osseous processes. Imaging with magnetic resonance imaging (MRI) or computed tomography (CT) typically shows multiple fluid levels. Bone lesions are not typically evaluated with ultrasound as the sound waves are not able to penetrate the cortex. If however the cortex is thinned, expanded, or disrupted, ultrasound can identify primary and secondary bone tumors. Ultrasound is often used as a first imaging study for evaluation of palpable superficial masses. Recognition of a lesion to be originating from the bone rather than soft tissue and identification of mobile fluid/fluid levels can suggest the diagnosis of aneurysmal bone cyst and direct the patient to the appropriate treatment. Little has been written in the literature about the sonographic appearance of ABC. We describe the ultrasound, radiographic, and MRI appearance of an aneurysmal bone cyst in the distal fibula. 2. Case Report A 34-year-old man presented to his family practitioner with a two-month history of swelling and discomfort in the left lateral lower leg just above his ankle. There was no preceding history of trauma. Physical examination revealed soft tissue fullness at the junction of the proximal two-thirds and distal one-third of the left fibula which was painful to touch. The patient was sent for an ultrasound for evaluation and possibly to aspirate a presumed ganglion cyst. Ultrasound was performed using a General Electric Healthcare Logiq E9 linear ML 6–15?MHz transducer (GE Healthcare Wauwatosa, WI). A cortically based lesion was noted arising from the anterolateral cortex of the fibula with elevation of the periosteum and a thin rim of echogenicity surrounding the mass, presumed to be a thin shell of bone (Figure 1) which appeared intact without adjacent soft tissue mass. Two fluid-fluid
On the altitude dependence of the spectral characteristics of decametre-wavelength E region backscatter and the relationship with optical auroral forms
S. E. Milan, M. Lester, N. Sato,H. Takizawa
Annales Geophysicae (ANGEO) , 2001,
Abstract: Observations of E region backscatter by the Ice-land East SuperDARN HF radar from the 30 minute period 2330 to 2400 UT on 13 September 1999 are presented, along with simultaneous observations of auroral luminosity from two all-sky cameras. Interferometric techniques are employed to estimate the altitude of origin of each echo observed by the radar. Under investigation is a region of backscatter which is L-shell aligned and exists in a region of low auroral luminosity bounded to the north and the south by two auroral arcs. The spectral characteristics of the backscatter fall into three main populations: broad, low Doppler shift spectra; narrow, high Doppler shift spectra; and exceptionally narrow, low Doppler shift spectra. The first two populations are similar to type II and type I spectra observed with VHF radars, respectively. These populations scatter from near the peak of the E region. The high Doppler shift population appears to exist in a region of sub-critical electric field. The third population originates below the E region peak at altitudes between 80 and 100 km. We argue that a non-coherent scattering process is responsible for this backscatter. Key words. Ionosphere (auroral ionosphere; ionospheric irregularities)
Investigation of the relationship between optical auroral forms and HF radar E region backscatter
S. E. Milan,M. Lester,N. Sato,H. Takizawa
Annales Geophysicae (ANGEO) , 2003,
Abstract: The SuperDARN HF radars have been employed in the past to investigate the spectral characteristics of coherent backscatter from L-shell aligned features in the auroral E region. The present study employs all-sky camera observations of the aurora from Husafell, Iceland, and the two SuperDARN radars located on Iceland, Tykkvib r and Stokkseyri, to determine the optical signature of such backscatter features. It is shown that, especially during quiet geomagnetic conditions, the backscatter region is closely associated with east-west aligned diffuse auroral features, and that the two move in tandem with each other. This association between optical and radar aurora has repercussions for the instability mechanisms responsible for generating the E region irregularities from which radars scatter. This is discussed and compared with previous studies investigating the relationship between optical and VHF radar aurora. In addition, although it is known that E region backscatter is commonly observed by SuperDARN radars, the present study demonstrates for the first time that multiple radars can observe the same feature to extend over at least 3 h of magnetic local time, allowing precipitation features to be mapped over large portions of the auroral zone. Key words: Ionosphere (particle precipitation; plasma waves and instabilities)
The spectral characteristics of E-region radar echoes co-located with and adjacent to visual auroral arcs
S. E. Milan,N. Sato,M. Lester,T. K. Yeoman
Annales Geophysicae (ANGEO) , 2003,
Abstract: Simultaneous all-sky camera and HF radar observations of the visual and E-region radar aurora in the west-ward electrojet suggest a close relationship between a pair of parallel east-west-aligned auroral arcs, separated by ~ 30 km, and a region of strong radar backscatter. Poleward of this a broader region of radar backscatter is observed, though the spectral characteristics of the echoes in these two regions differ considerably. We suggest that the visual aurorae and their radar counterparts are produced in a region of upward field-aligned current (FAC), whereas the backscatter poleward of this is associated with downward FAC. Relatively low electric fields ( ~ 10 mV m-1) are observed in the vicinity of the arc system, suggesting that in this case, two-stream waves are not directly generated through the electrodynamics of the arc. Rather, the generation of irregularities is most probably associated with the gradient drift instability operating within horizontal electron density gradients produced by the filamentary nature of the arc FAC system. The observation of high Doppler shift echoes superimposed on slow background flow within the region of backscatter poleward of the visual aurora is argued to be consistent with previous suggestions that the ion-acoustic instability threshold is reduced in the presence of upwelling thermal electrons carrying downward FAC. Key words. Ionosphere (auroral ionosphere; ionospheric irregularities; particle precipitation)
E-region echo characteristics governed by auroral arc electrodynamics
S. E. Milan,N. Sato,M. Lester,Y. Murata
Annales Geophysicae (ANGEO) , 2003,
Abstract: Observations of a pair of auroral arc features by two imagers, one ground- and one space-based, allows the associated field-aligned current (FAC) and electric field structure to be inferred. Simultaneous observations of HF radar echoes provide an insight into the irregularity-generating mechanisms. This is especially interesting for the E-region echoes observed, which form the focus of our analysis, and from which several conclusions can be drawn, summarized as follows. Latitudinal variations in echo characteristics are governed by the FAC and electric field background. Particularly sharp boundaries are found at the edges of auroral arcs. Within regions of auroral luminosity, echoes have Doppler shifts below the ion-acoustic speed and are proportional to the electric field, suggesting scatter from gradient drift waves. Regions of downward FAC are associated with mixed high and low Doppler shift echoes. The high Doppler shift component is greatly in excess of the ion-acoustic speed, but seems to be commensurate with the driving electric field. The low Doppler shift component appears to be much depressed below expectations. Key words. Ionosphere (ionospheric irregularities; electric fields and currents)
Potential impact of pharmaceuticals on environmental health
Jones Oliver A.H.,Voulvoulis Nick,Lester John N.
Bulletin of the World Health Organization , 2003,
Quantum Monte Carlo methods for the solution of the Schroedinger equation for molecular systems
Alán Aspuru-Guzik,William A. Lester Jr
Physics , 2002,
Abstract: This is a book chapter soon to appear (2002) in the "Handbook for Numerical Analysis" volume dedicated to "Computational Chemistry" edited by Claude Le Bris. The series editors are P.G. Ciarlet and J. L. Lions. [North Holland/Elservier]. This review deals with some of the methods known under the umbrella term quantum Monte Carlo (QMC), specifically those that have been most commonly used for electronic structure.
Page 1 /198875
Display every page Item

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