65 results on '"Craig Walker"'
Search Results
52. Same dose of drug, different magnitude of effect?
- Author
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Craig, Walker
- Subjects
Immunoglobulin Fab Fragments ,Dose-Response Relationship, Drug ,Risk Factors ,Abciximab ,Coronary Thrombosis ,Drug Administration Routes ,Antibodies, Monoclonal ,Humans ,Platelet Aggregation Inhibitors - Published
- 2010
53. Will the transradial approach become the preferred approach in subclavian artery stenting?
- Author
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Craig, Walker
- Subjects
Radial Artery ,Humans ,Stents ,Coronary Artery Disease ,Angioplasty, Balloon, Coronary - Published
- 2010
54. Precise geodesy with the Very Long Baseline Array
- Author
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Leonid Petrov, Ed Fomalont, Chopo Ma, Claudia C. Carabajal, David Gordon, R. Craig Walker, Dan MacMillan, and John Gipson
- Subjects
Geodetic datum ,FOS: Physical sciences ,Geodesy ,Motion (physics) ,Geophysics (physics.geo-ph) ,Physics - Geophysics ,Geophysics ,Geochemistry and Petrology ,Very-long-baseline interferometry ,Antenna tilt ,Millimeter ,Computers in Earth Sciences ,Terrestrial reference frame ,Very Long Baseline Array ,Geology - Abstract
We report on a program of geodetic measurements between 1994 and 2007 which used the Very Long Baseline Array and up to 10 globally distributed antennas. One of the goals of this program was to monitor positions of the array at a 1 millimeter level of accuracy and to tie the VLBA into the International Terrestrial Reference Frame. We describe the analysis of these data and report several interesting geophysical results including measured station displacements due to crustal motion, earthquakes, and antenna tilt. In terms of both formal errors and observed scatter, these sessions are among the very best geodetic VLBI experiments., Published in the Journal of Geodesy; 18 pages, 10 figures
- Published
- 2008
55. High Frequency VLBI Imaging of the Jet Base of M87
- Author
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W. Junor, Chun Ly, and R. Craig Walker
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Physics ,Brightness ,Jet (fluid) ,Spectral index ,010308 nuclear & particles physics ,Orientation (computer vision) ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Space and Planetary Science ,0103 physical sciences ,Very-long-baseline interferometry ,Angular resolution ,High Energy Physics::Experiment ,010303 astronomy & astrophysics ,Schwarzschild radius ,Image resolution - Abstract
VLBA and Global VLBI observations of M87 at 43 GHz, some new and some previously published, are used to study the structural evolution of the jet with a spatial resolution of under 100 Schwarzschild radii. The images, taken between 1999 and 2004, have an angular resolution of 0.00043" x 0.00021". An edge-brightened jet structure and an indication of a large opening angle at the jet base are seen in all five epochs. In addition, a probable counter-jet is seen in the latter three epochs. A 22 GHz VLBA image also confirms many of the structures seen at the higher frequency, including the counter-jet. A comparison of the counter-jet flux density at 22 and 43 GHz reveals that it is not free-free absorbed at these frequencies. Attempts to obtain speeds from the proper motions of jet and counter-jet components indicate that these observations are undersampled. The closest pair of images gives apparent speeds of 0.25 to 0.40c for the jet and 0.17c for the counter-jet. These speeds should be treated as lower limits because of possible errors in associating components between epochs. If they are real, they indicate that the jet is oriented 30-45 degrees from the line-of-sight and that the component speeds along the jet are 0.3-0.5c. Using the jet orientation derived from proper motions, the spectral index of the the counter-jet, and a jet-to-counter-jet brightness ratio of 14.4, the inferred bulk flow is 0.6-0.7c, which, given the considerable uncertainties in how to measure the brightness ratio, is not significantly larger than the component speed., 16 pages, 1 table, 3 color figures, accepted to the Astrophysical Journal
- Published
- 2007
56. Novel excitatory Conus peptides define a new conotoxin superfamily
- Author
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Elsie C, Jimenez, Reshma P, Shetty, Marcelina, Lirazan, Jean, Rivier, Craig, Walker, Fe C, Abogadie, Doju, Yoshikami, Lourdes J, Cruz, and Baldomero M, Olivera
- Subjects
Neurotoxins ,Rana pipiens ,Action Potentials ,Mollusk Venoms ,In Vitro Techniques ,Electrophysiology ,Mice ,Sequence Analysis, Protein ,Goldfish ,Multigene Family ,Animals ,Biological Assay ,Peripheral Nerves ,Conotoxins ,Muscle, Skeletal ,Peptides ,Gene Library - Abstract
A new class of Conus peptides, the I-superfamily of conotoxins, has been characterized using biochemical, electrophysiological and molecular genetic methods. Peptides in this superfamily have a novel pattern of eight Cys residues. Five peptides that elicited excitatory symptomatology, r11a, r11b, r11c, r11d and r11e, were purified from Conus radiatus venom; four were tested on amphibian peripheral axons and shown to elicit repetitive action potentials, consistent with being members of the 'lightning-strike cabal' of toxins that effect instant immobilization of fish prey. A parallel analysis of Conus cDNA clones revealed a new class of conotoxin genes that was particularly enriched (with 18 identified paralogues) in a Conus radiatus venom duct library; several C. radiatus clones encoded the excitatory peptides directly characterized from venom. The remarkable diversity of related I-superfamily peptides within a single Conus species is unprecedented. When combined with the excitatory effects observed on peripheral circuitry, this unexpected diversity suggests a corresponding molecular complexity of the targeted signaling components in peripheral axons; the I-conotoxin superfamily should provide a rich lode of pharmacological tools for dissecting and understanding these. Thus, the I-superfamily conotoxins promise to provide a significant new technology platform for dissecting the molecular components of axons.
- Published
- 2003
57. Directly connecting the Very Long Baseline Array
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R. Craig Walker, Gareth Hunt, and Jonathan D. Romney
- Subjects
Computer science ,business.industry ,Electrical engineering ,Instrumentation (computer programming) ,Wideband ,Antenna (radio) ,Data rate ,business ,Very Long Baseline Array - Abstract
At present, the signals received by the 10 antennas of the Very Long Baseline Array (VLBA) are recorded on instrumentation tapes. These tapes are then shipped from the antenna locations - distributed across the mainland USA, the US Virgin Islands, and Hawaii - to the processing center in Socorro, New Mexico. The Array operates today at a mean sustained data rate of 128 Mbps per antenna, but peak rates of 256 Mbps and 512 Mbps are also used. Transported tapes provide the cheapest method of attaining these bit rates. The present tape system derives from wideband recording techniques dating back to the late 1960s, and has been in use since the commissioning of the VLBA in 1993. It is in need of replacement on a time scale of a few years. Further, plans are being developed which would increase the required data rates to 1 Gbps in 5 years and 100 Gbps in 10 years. With the advent of higher performance networks, it should be possible to transmit the data directly to the processing center. However, achieving this connectivity is complicated by the remoteness of the antennas
- Published
- 2002
- Full Text
- View/download PDF
58. Inhibition of ultraviolet B radiation-induced interleukin 10 expression in murine keratinocytes by selenium compounds
- Author
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R. C. Mckenzie, T.S. Rafferty, John A. A. Hunter, Geoffrey J. Beckett, and Craig Walker
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Keratinocytes ,Ultraviolet Rays ,medicine.medical_treatment ,chemistry.chemical_element ,Dermatology ,Cell Line ,Mice ,Immune system ,Sodium Selenite ,medicine ,Animals ,Selenium Compounds ,Selenomethionine ,Immunity, Cellular ,biology ,Interleukin ,Molecular biology ,Immunohistochemistry ,Interleukin-10 ,Interleukin 10 ,medicine.anatomical_structure ,Cytokine ,chemistry ,Biochemistry ,biology.protein ,Antibody ,Keratinocyte ,Immunostaining ,Selenium - Abstract
SummaryBackground Selenium is an essential trace nutrient necessary for the normal function of the immune system. Selenium compounds protect mice against ultraviolet (UV) B-induced tumours, probably by preventing oxidative damage to the host skin cells and to the host immune system. One possible mechanism of protection is that selenium can prevent oxidative stress-induced release of cytokines such as interleukin (IL)-10, which could suppress cell-mediated immunity. Objectives To determine whether selenium compounds can inhibit UVB induction of IL-10 protein in murine keratinocytes. Methods The murine keratinocyte cell line PAM 212 was treated with or without selenomethionine (50–200 nmol L−1) or sodium selenite (1–50 nmol L−1) for 24 h before exposure to 200 J m−2 UVB. The cells were stained with an antibody to IL-10, 24 h after irradiation. Results Preincubation with both selenium compounds inhibited UVB induction of IL-10 immunostaining, although selenomethionine was more effective. Pretreatment with 200 nmol L−1 selenomethionine decreased IL-10 immunostaining to levels seen in the unirradiated controls. Conclusions The protective effects of selenium against UVB-induced skin cancer in murine models may result, in part, from its ability to inhibit release of cytokines that are capable of suppressing cell-mediated immunity.
- Published
- 2002
59. Virtual Tutor: A System for Deploying Digital Libraries in Classrooms
- Author
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Greg MacPherson, Innes Martin, Brian Robertson, Craig Walker, Hywel Braddick, and Joemon M. Jose
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Multimedia ,Summative assessment ,Computer science ,Human–computer interaction ,ComputingMilieux_COMPUTERSANDEDUCATION ,Systems architecture ,Educational technology ,Collaborative learning ,TUTOR ,computer.software_genre ,Digital library ,computer ,computer.programming_language - Abstract
In this paper, we introduce a collaborative learning environment called Virtual Tutor for exploiting valuable digital libraries for teaching and learning. Virtual Tutor facilitates the building of online lectures and their provision. It also supports collaborative and explorative learning. We describe the architecture of the system and its functionality. A summative evaluation is conducted on the system. The paper concludes by comparing the Virtual Tutor functionality with similar approaches and highlighting the strengths of the Virtual Tutor design.
- Published
- 2002
- Full Text
- View/download PDF
60. Hamstring muscle strain injury caused by isokinetic testing
- Author
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Ameer Ibrahim, Elizabeth Steet, John Orchard, Michael Houang, Luke Rigney, and Craig Walker
- Subjects
Adult ,Male ,Football ,Pain ,Physical Therapy, Sports Therapy and Rehabilitation ,Physical examination ,Biceps ,Recurrence ,medicine ,Eccentric ,Humans ,Orthopedics and Sports Medicine ,Semitendinosus muscle ,Muscle, Skeletal ,Morning ,Hamstring injury ,medicine.diagnostic_test ,business.industry ,Recovery of Function ,medicine.disease ,Magnetic Resonance Imaging ,Tenderness ,Anesthesia ,Exercise Test ,Physical Endurance ,Sprains and Strains ,medicine.symptom ,business ,Hamstring ,Leg Injuries ,Muscle Contraction - Abstract
The patient was a 25-year-old (height: 183 cm, weight: 86 kg) professional rugby league winger. He had suffered a recurrent episode of a left hamstring (biceps femoris) injury at a training drill late in the season (Day 0). This occurred suddenly while changing direction at pace. The player felt the degree of pain when injured to be very similar to his previous episode earlier in the season, which had taken 2 weeks to resolve. The initial clinical signs were consistent with a routine low-grade hamstring strain, with local tenderness in the midlateral hamstring and moderately decreased stretch and power on the left side compared with the right. He was ruled out for a scheduled match on Day 1. On Days 2–3 the player did not undertake any running activity and was treated with physiotherapy and ice. Over this period the player was pain free on walking. On the morning of Day 4, the player had an MRI scan that confirmed a grade 1 strain of the left biceps femoris muscle (Figure 1). The length of the right hamstring was visualized by the scan and was normal. On the afternoon of Day 4, the player underwent a concentric and eccentric bilateral isokinetic strength test using a KinCom dynamometer (Chattecx; Chattanooga, TN, U.S.A.). He had no previous experience with using this machine. The initial protocol was to test endurance and was performed in a seated position with a slow acceleration phase. There were 15 repetitions bilaterally of knee extension and then flexion at 180° per second. He completed this section of the test, but felt mild pain when testing his left hamstring and mild-to-moderate pain when testing his right hamstring muscle. He had not previously injured the right hamstring. Due to the pain, he did not undergo a maximal peak torque test that was planned to follow. After the test he felt pain on walking in both hamstring muscles and felt as though the test may have worsened his left hamstring strain and also caused a similar injury in his right hamstring muscle. The results of the testing are detailed in Table 1. On day 5, examination revealed very similar findings in the right and left hamstring muscle, with local tenderness, slightly reduced stretch, reduced power on clinical examination, and pain on resisted contraction. He continued physiotherapy treatment and ice, but was not prescribed nonsteroidal antiinflammatory drugs (NSAIDs). At this stage, the diagnosis was resolving left hamstring strain and probable muscle soreness in the right hamstring following the isokinetic testing. On day 7 the player attempted a light jog and felt sore in both hamstring muscles. Because of this symptom, he was told not to attempt further running and was ruled out of the weekend’s match, scheduled for day 10. On day 14 the player underwent an MRI scan, which showed signs of the original left hamstring strain with signal intensity that was markedly reduced. It also showed an unexpected finding of a strain of the right hamstring muscle of much greater signal intensity than the left side (Figure 2). The right hamstring strain involved 20% of the cross-sectional area of the semitendinosus muscle over a distance of 10 cm. On day 17 (17 days after the left hamstring injury and 13 days after the right hamstring injury) he successfully played a match, and had no further incidence of hamstring injury for the remainder of the season.
- Published
- 2001
61. FC020 Leukaemia inhibitory factor: Induction in the early phase of allergic contact dermatitis
- Author
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R.D. Aldridge, R.C. Mckenzie, S.G. Keohane, J.A.A. Hunter, Craig Walker, and Jacek C Szepietowski
- Subjects
Infectious Diseases ,business.industry ,Immunology ,Medicine ,Dermatology ,Inhibitory postsynaptic potential ,business ,medicine.disease ,Early phase ,Allergic contact dermatitis - Published
- 1997
- Full Text
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62. Case-control analysis of risk factors for presence of aortic stenosis in adults (age 50 years or older)
- Author
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E. Francis Cook, Lee Goldman, Peter M. Hoagland, Margaret Flatley, and Craig Walker
- Subjects
Aortic valve ,Male ,Risk ,medicine.medical_specialty ,Arteriosclerosis ,Coronary Disease ,Coronary artery disease ,Diabetes Complications ,Internal medicine ,Diabetes mellitus ,Statistical significance ,medicine ,Humans ,cardiovascular diseases ,Risk factor ,Diagnosis-Related Groups ,Aged ,business.industry ,Elevated serum cholesterol ,Smoking ,Aortic Valve Stenosis ,Middle Aged ,medicine.disease ,Stenosis ,medicine.anatomical_structure ,Cholesterol ,Hypertension ,Cardiology ,Case control analysis ,Female ,Cardiology and Cardiovascular Medicine ,business - Abstract
To analyze whether atherosclerotic risk factors, including systemic hypertension, an elevated serum cholesterol level, smoking and diabetes, were associated with the presence of aortic stenosis (AS) in adults, 105 adults who had AS without coronary artery disease (CAD) were compared with 110 control subjects who had other types of valvular disease, 170 control subjects who underwent catheterization and had neither valvular disease nor CAD, and 269 matched control subjects who underwent general surgery. When using each control group separately or in combination, no risk factor showed consistent evidence of a significant association with the development of AS. If the true magnitudes of these associations are of the order previously reported for the development of CAD, the power of our study for detecting statistical significance ranges from 56 to 99%. In a supplemental analysis, 45 cases with both AS and CAD did not have a higher prevalence of risk factors than cases without CAD. Although a weak association between atherosclerotic risk factors and AS cannot be excluded, any such association is unlikely to be as strong as for predicting CAD.
- Published
- 1985
63. A simulation approach to analysis of emergency services and trauma center management
- Author
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Thomas D. Clark and Craig Walker Waring
- Subjects
Computer science ,Trauma center ,Scheduling (production processes) ,Operations management ,In patient ,Simulation ,Scheduling (computing) - Abstract
The operation of a hospital trauma center and associated transportation facility is discussed in this paper. A SLAM simulation model of the system is explained and example experiments with it discussed. Results indicate that significant improvement in patient service can be made through alternative staff scheduling patterns. Patient flow is particularly sensitive to the shift scheduling of physicians.
- Published
- 1987
- Full Text
- View/download PDF
64. The Structure and Dynamics of the Subparsec Jet in M87 Based on 50 VLBA Observations over 17 Years at 43 GHz.
- Author
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R. Craig Walker, Philip E. Hardee, Frederick B. Davies, Chun Ly, and William Junor
- Subjects
- *
EXTRAGALACTIC jets (Astrophysics) , *TOROIDAL magnetic circuits , *INTERFEROMETRY , *MAGNETIC fields - Abstract
The central radio source in M87 provides the best opportunity to study jet formation because it has a large angular size for the gravitational radius of the black hole and has a bright jet that is well resolved by very long baseline interferometry observations. We present intensive monitoring observations from 2007 and 2008, plus roughly annual observations that span 17 years, all made with the the Very Long Baseline Array at 43 GHz with a resolution of about 30 by 60RS. Our high dynamic range images clearly show the wide opening angle structure and the counterjet. The jet and counterjet are nearly symmetric in the inner 1.5 mas (0.12 pc in projection), with both being edge brightened. Both show deviations from parabolic shape in the form of an initial rapid expansion and subsequent contraction followed by further rapid expansion and, beyond the visible counterjet, subsequent collimation. Proper motions and counterjet/jet intensity ratios both indicate acceleration from apparent speeds of ≲0.5c to ≳2c in the inner ∼2 mas and suggest a helical flow. The jet displays a sideways shift with an approximately 8–10 yr quasi-periodicity. The shift propagates outward nonballistically and significantly more slowly than the flow speed revealed by the fastest-moving components. Polarization data show a systematic structure with magnetic field vectors that suggest a toroidal field close to the core. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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65. Evidence for superluminal motion on kiloparsec scales in 3C 120
- Author
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J. M. Benson, Mark Walker, and R. Craig Walker
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Physics ,Interferometry ,Superluminal motion ,Classical mechanics ,Flow velocity ,Space and Planetary Science ,Astronomy and Astrophysics ,Angular velocity ,Astrophysics - Published
- 1988
- Full Text
- View/download PDF
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