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Biomedical subjects

J Arthur

Publications and source records attributed to J Arthur.

At least 19 recordsLinked to original sources
PubMed2005

Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb.

The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.

Journal Article↗
PubMed2005

Atomic-scale visualization of inertial dynamics.

The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.

Journal Article↗
PubMed2005

Clocking femtosecond X rays.

Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.

Journal Article↗
PubMed2004

Future possibilities of the Linac Coherent Light Source.

A study of the potential for the development of the Linac Coherent Light Source (LCLS) beyond the specifications of the baseline design is presented. These future developments include delivery of X-ray pulses in the 1 fs regime, extension of the spectral range, increase of the FEL power, exploitation of the spontaneous emission, and a more flexible time structure. As this potential is exploited, the LCLS can maintain its role as a world-leading instrument for many years beyond its commissioning in 2008 and initial operation as the world's first X-ray free-electron laser.

Journal Article↗
PubMed2004

Increasing the accuracy of operative coding.

INTRODUCTION: Operative codes provide a readily retrievable record of operative procedures and interventions and are invaluable in performance of clinical audit and research. In most hospitals, coding is performed by coding clerks who depend on legible complete operative notes for coding. In others, coding is by the operator/surgeon. The aim of this audit was to determine the impact of hand-written and typed operative notes on accuracy of coding as well as deciding if the operator is the better coder. METHODS: A total of 200 operations/procedures performed by one surgical firm were randomised, prospectively, into hand-written (HN, 100) and template-based typed (TN, 100) operation notes. Each procedure was coded by the operator/surgeon as well as by the coding clerk. The results were compared for error, incomplete and complete codes. RESULTS: Coding clerks were found to be better coders with 97% of TN and 85% of HN coded completely compared to 48% and 62%, respectively, by operators. There were more incomplete codes for HN compared to TN (15% versus 6% for coders and 62% versus 53% for operators). There were no error codes for both groups. CONCLUSIONS: These results suggest that the quality of coded information is poorer if operation notes are hand-written rather than typed, with template-based mandatory fields in typed notes possibly acting as an aide-memoir in generating complete, accurate notes. In the absence of formal training for clinicians, coding of procedures should probably be left to coding clerks.

Forms and Records Control↗
PubMed2001

Nature of e(g) electron order in La(1-x)Sr(1+x)MnO(4).

X-ray scattering measurements of the low-temperature structure of La(1-x)Sr(1+x)MnO(4) ( 0.33< or =x< or =0.67) indicate the existence of three distinct regions: a disordered phase (x<0.4), a charge-ordered phase (x> or =0.5), and a mixed phase (0.4< or =x<0.5). For x>0.5, the modulation vector associated with the charge order is incommensurate with the lattice and depends linearly on the concentration of e(g) electrons. The primary superlattice reflections are strongly suppressed along the modulation direction and the higher harmonics are weak, implying the existence of a largely transverse and nearly sinusoidal structural distortion, consistent with a charge-density wave of the e(g) electrons.

Journal Article↗
PubMed2000

When is reduced-compression bandaging safe and effective?

During a one-year period 44 patients were treated with reduced-compression bandaging in the vascular unit at a district general hospital. Twenty patients with venous ulcers were referred from community leg ulcer clinics because they could not tolerate standard compression bandaging (group 1). A further 24 patients had mixed aetiology leg ulcers (group 2), and high-compression bandaging was not attempted because of significant peripheral vascular disease (ankle brachial pressure index < 0.8). Forty-two patients tolerated reduced-compression bandaging without discomfort or skin pressure changes. Healing was achieved in 32 patients (13 in group 1 and 19 in group 2). All non-healed ulcers were considered smaller at the time of final follow-up, and had less exudate. Reduced-compression bandaging has been shown to be effective and well tolerated by patients with venous ulcers who cannot comply with high-compression bandaging. With close supervision, it is safe to use in patients with significant peripheral vascular disease.

Adult↗
PubMed1999

A study of primary neuronal infection by mutants of herpes simplex virus type 1 lacking dispensable and non-dispensable glycoproteins.

Cultures of primary rat dorsal root ganglia neurones were inoculated with various doses of herpes simplex virus mutants deficient in glycoproteins B, D, H, C, G, E, I or J, and the proportion of infected neurones was determined. The behaviour of these mutants on primary neurones was broadly similar to their behaviour on fibroblasts or epithelial cells. Thus, virions lacking the 'nondispensable' glycoproteins B, D or H were incapable of infecting primary neurones, whereas mutants lacking glycoproteins G, E, I or J infected primary neurones with the same efficiency as wild-type virions. Two independently derived mutants lacking gC displayed a marginal phenotype, infecting neurones with a five- to tenfold reduced efficiency relative to wild-type virus and relative to non-neuronal cells in the same cultures. We conclude that the virion glycoprotein requirements for infection of mammalian neurones are similar to those required for infection of fibroblasts and epithelial cells but that glycoprotein C may enhance infection of neurones.

Animals↗
PubMed1997

Transduction of murine and human tumors using recombinant adenovirus vectors.

BACKGROUND: Most cytokine-based cancer gene therapy clinical trials have used labor-intensive, retrovirus-mediated strategies resulting in unpredictable gene expression. Recombinant AdV vectors were evaluated for easier, more reproducible gene transfer into 12 human melanoma, 2 murine fibrosarcomas, and 8 other tumor cell lines. METHODS: AdV vectors contained a reporter (Escherichia coli beta-galactosidase or firefly luciferase) or cytokine gene (human interleukin-2 [IL-2] or IL-7). Transduction efficiencies and expression levels were assessed by histochemical staining, flow cytometry, polymerase chain reaction, fluorometry, and enzyme-linked immunosorbent assay. Tumorigenicity was determined by subcutaneous injection of cells into syngeneic mice. RESULTS: All cell lines studied were transduced with AdV. Most cell lines exhibited 100% transduction efficiencies (by flow cytometry) at multiplicities of infection (MOI) epsilon 10. Gene expression correlated linearly with MOI, but a cytopathic effect was observed at MOI > 100 with all vectors. Nanogram gene expression levels were routinely achieved. Irradiation (30 Gy) minimally affected expression levels. Tumorigenicity of AdV-IL-2-transduced fibrosarcoma cells in mice was inversely related to IL-2 production. A majority of mice that rejected their tumor challenge were immune to tumor rechallenge. CONCLUSIONS: E1-deleted AdV vectors may prove useful in generating tumor vaccines ex vivo with high, transient cytokine expression levels.

Adenoviridae↗
PubMed1995

Efficacy, safety, and immunogenicity of a meningococcal group B (15:P1.3) outer membrane protein vaccine in Iquique, Chile. Chilean National Committee for Meningococcal Disease.

A meningococcal group B (15:P1.3) outer membrane protein vaccine was tested for efficacy in a randomized, double-blind controlled study in Iquique, Chile. A total of 40 811 volunteers, ages 1-21 years, enrolled in the study. Volunteers received two doses of vaccine six weeks apart by jet injector. Both the experimental vaccine and the control vaccine (Menomune, A, C, Y and W135 meningococcal polysaccharide vaccine) were well tolerated with minor side-effects. Active surveillance for suspected cases of meningococcal disease was conducted for 20 months in Iquique. Eighteen cases of group B meningococcal disease were confirmed during the 20 months. Efficacy was estimated to be 51% (p = 0.11) for all ages combined. In children aged 1-4 no protection was evident, but in volunteers aged 5-21 vaccine efficacy was 70% (p = 0.045). The IgG antibody response by ELISA was characterized by a large booster effect after the second dose, followed by a substantial drop in antibody levels by 6 months. The youngest children had the highest responses. The bactericidal antibody response, on the other hand, was characterized by the lack of a significant booster response, higher responses in the older children, and an increase in the geometric mean titer in the later months of the study in the older children.

Adolescent↗
PubMed1995

Characterization of a gene encoding a cysteine-rich keratin associated protein synthesized late in rabbit hair follicle differentiation.

Many different cysteine-rich proteins are synthesized during hair follicle differentiation, forming part of the interstitial matrix between bundles of intermediate filaments. We have isolated a rabbit gene (rKAP4L), a member of a multigene family that encodes a small cysteine-rich hair keratin associated protein. This is the first complete gene sequence for this family. The rKAP4L gene is expressed in the cortex of rabbit pelage hair follicles at a late stage of hair follicle differentiation, well after the synthesis of the other major hair proteins, the intermediate filament and glycine/tyrosine-rich keratin associated proteins, has commenced. The protein contains 36 mol % cysteine, with a molecular size of 13593 daltons, and its sequence appears to be based on a pentapeptide repeat. It is predicted to adopt a folded conformation characterized by beta-turns interspersed with short stretches of beta-sheet or random coil.

Amino Acid Sequence↗
PubMed1994

Clinical utility of digital dobutamine stress echocardiography in the noninvasive evaluation of coronary artery disease.

Exercise electrocardiography is an established mode of evaluation for patients with suspected coronary artery disease. It also provides prognostic information and guides therapeutic management in patients with established disease. However, some patients are unable to exercise because of orthopedic problems, neurologic diseases, peripheral vascular disease, or deconditioning. In the past, these patients have been referred for angiography to help assess their disease. Recently, however, new techniques to assess myocardial perfusion and/or function, including stress echocardiography, have been used in the noninvasive assessment of coronary artery disease in this group of patients. Echocardiography has been used in combination with different drugs, including dobutamine, dipyridamole, and adenosine. Dobutamine is probably the single most studied drug for stress echocardiography. Dobutamine stress echocardiography is a safe, feasible, and valuable technique for evaluating coronary artery disease.

Clinical Trials as Topic↗
PubMed1994

The prevalence of ST-segment depression on ambulatory electrocardiographic monitoring during daily life in high-risk asymptomatic police officers.

BACKGROUND: In individuals with no known ischaemic heart disease, the prevalence and significance of ST-segment depression on ambulatory electrocardiographic monitoring is unclear. We therefore determined the prevalence of ST-segment depression among middle-aged male police officers, an occupational group in whom an increased risk of ischaemic heart disease has been reported, who also had multiple individual coronary risk factors but no known ischaemic heart disease. METHODS: Full-time male police offices aged 45 years or more with at least two coronary risk factors but no known ischaemic heart disease performed a 24h ambulatory electrocardiographic monitor, timed to include a shift of work. The number and duration of episodes of ST-segment depression were determined. In those in whom ST-segment depression was detected, exercise thallium scintigraphy and repeat 24h ambulatory electrocardiographic monitoring were performed. RESULTS: The prevalence of ST-segment depression on 24h ambulatory electrocardiographic monitoring, including an 8h period of normal work, was 3.4% (95% confidence interval 1.3-8.3%). Exercise thallium scintigraphy was carried out in those in whom ST-segment depression had been detected. Despite two participants developing ST-segment depression during exercise, no evidence of myocardial ischaemia was observed on the perfusion scan. Therefore, the prevalence of ST-segment depression on ambulatory electrocardiographic monitoring in this asymptomatic but high-risk population was low and, when it did occur, no exercise-induced myocardial ischaemia was observed. CONCLUSION: These results suggest that ST-segment depression on ambulatory electrocardiographic monitoring in asymptomatic subjects may not represent myocardial ischaemia. The use of this parameter to screen asymptomatic populations for ischaemic heart disease is therefore highly questionable.

Activities of Daily Living↗