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R Chapman

Publications and source records attributed to R Chapman.

At least 19 recordsLinked to original sources
PubMed2006

A photometric redshift of z = 6.39 +/- 0.12 for GRB 050904.

Gamma-ray bursts (GRBs) and their afterglows are the most brilliant transient events in the Universe. Both the bursts themselves and their afterglows have been predicted to be visible out to redshifts of z approximately 20, and therefore to be powerful probes of the early Universe. The burst GRB 000131, at z = 4.50, was hitherto the most distant such event identified. Here we report the discovery of the bright near-infrared afterglow of GRB 050904 (ref. 4). From our measurements of the near-infrared afterglow, and our failure to detect the optical afterglow, we determine the photometric redshift of the burst to be z = 6.39 - 0.12 + 0.11 (refs 5-7). Subsequently, it was measured spectroscopically to be z = 6.29 +/- 0.01, in agreement with our photometric estimate. These results demonstrate that GRBs can be used to trace the star formation, metallicity, and reionization histories of the early Universe.

Journal Article↗
PubMed2005

An origin in the local Universe for some short gamma-ray bursts.

Gamma-ray bursts (GRBs) divide into two classes: 'long', which typically have initial durations of T90 > 2 s, and 'short', with durations of T90 < 2 s (where T90 is the time to detect 90% of the observed fluence). Long bursts, which on average have softer gamma-ray spectra, are known to be associated with stellar core-collapse events-in some cases simultaneously producing powerful type Ic supernovae. In contrast, the origin of short bursts has remained mysterious until recently. A subsecond intense 'spike' of gamma-rays during a giant flare from the Galactic soft gamma-ray repeater, SGR 1806-20, reopened an old debate over whether some short GRBs could be similar events seen in galaxies out to approximately 70 Mpc (refs 6-10; redshift z approximately 0.016). Shortly after that, localizations of a few short GRBs (with optical afterglows detected in two cases) have shown an apparent association with a variety of host galaxies at moderate redshifts. Here we report a correlation between the locations of previously observed short bursts and the positions of galaxies in the local Universe, indicating that between 10 and 25 per cent of short GRBs originate at low redshifts (z < 0.025).

Journal Article↗
PubMed2004

Characterization of proton and heavier ion acceleration in ultrahigh-intensity laser interactions with heated target foils.

Proton and heavy ion acceleration in ultrahigh intensity ( approximately 2 x 10(20) W cm(-2) ) laser plasma interactions has been investigated using the new petawatt arm of the VULCAN laser. Nuclear activation techniques have been applied to make the first spatially integrated measurements of both proton and heavy ion acceleration from the same laser shots with heated and unheated Fe foil targets. Fe ions with energies greater than 10 MeV per nucleon have been observed. Effects of target heating on the accelerated ion energy spectra and the laser-to-ion energy conversion efficiencies are discussed. The laser-driven production of the long-lived isotope (57 )Co (271 days) via a heavy ion induced reaction is demonstrated.

Journal Article↗
PubMed2004

Esomeprazole 20 mg on-demand is more acceptable to patients than continuous lansoprazole 15 mg in the long-term maintenance of endoscopy-negative gastro-oesophageal reflux patients: the COMMAND Study.

BACKGROUND: Symptom relief, through adherence to appropriate maintenance therapy, is the sole objective of treatment for patients with endoscopy-negative gastro-oesophageal reflux disease. AIM: To compare the efficacy of 'on-demand' treatment with esomeprazole 20 mg vs. continuous treatment with lansoprazole 15 mg daily in patients with endoscopy-negative gastro-oesophageal reflux disease. METHODS: Endoscopy-negative gastro-oesophageal reflux disease patients who achieved complete resolution of heartburn after short-term (2-4 weeks) treatment with esomeprazole 20 mg (n = 774) were randomized to receive either esomeprazole 20 mg on-demand (n =311) or lansoprazole 15 mg continuous daily treatment (n = 311) for 6 months. RESULTS: Significantly more patients were willing to continue taking esomeprazole on-demand than lansoprazole continuous therapy after 6 months (93% vs. 88%; P = 0.02). This superior outcome was achieved despite patients on esomeprazole requiring medication only 38% as often as those on lansoprazole, leading to direct cost savings of more than one-third (36%). Furthermore, patients receiving esomeprazole 20 mg on-demand were more satisfied with their treatment after 1 month compared with patients taking lansoprazole 15 mg continuously. CONCLUSIONS: In patients with endoscopy-negative gastro-oesophageal reflux disease, esomeprazole 20 mg on-demand is more acceptable to patients and is an economically more effective treatment than lansoprazole 15 mg continuously.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2004

Sentence memory of individuals with Down's syndrome and typically developing children.

BACKGROUND: Individuals with Down's syndrome (DS) have an auditory short-term memory span disproportionately shorter than the non-verbal mental age (MA). This study evaluated the Baddeley model's claim that verbal short-term memory deficits might arise from slower speaking rates (and thus less material rehearsed in a 2 s passive store) by using the sentence memory subtest of the Stanford-Binet. Previous work had shown digit span recall speaking rate to be comparable to the examiner's slow rate (one syllable per second) for both DS and language-matched participants. METHOD: Thirty individuals with DS were compared to two control groups [non-verbal MA-matched and mean length of utterance (MLU)-matched] on the sentence span and speaking rate for the longest verbatim recalled sentence. Sentence stimuli were presented at a normal speaking rate. RESULTS: The DS group had shorter sentence memory span than the MA-matched group and a faster, rather than slower, speaking rate (syllables per second) than the MLU-matched controls. CONCLUSIONS: Language production level accounted for a substantial portion of the variance in the sentence memory span in the DS group. Thus, language production skill, rather than speaking rate, predicts variability in verbal memory span.

Adolescent↗
PubMed2003

Demonstration of fusion-evaporation and direct-interaction nuclear reactions using high-intensity laser-plasma-accelerated ion beams.

Heavy-ion induced nuclear reactions in materials exposed to energetic ions produced from high-intensity (approximately 5 x 10(19) W/cm(2)) laser-solid interactions have been experimentally investigated for the first time. Many of the radionuclides produced result from the creation of "compound nuclei" with the subsequent evaporation of proton, neutron, and alpha particles. Results are compared with previous measurements with monochromatic ion beams from a conventional accelerator. Measured nuclide yields are used to diagnose the acceleration of ions from laser-ablated plasma to energies greater than 100 MeV.

Journal Article↗
PubMed2003

The "tamponade test" in the management of massive postpartum hemorrhage.

OBJECTIVE: Massive postpartum hemorrhage is a major cause of pregnancy-related death in the United States. To date there is no diagnostic test to identify those women with intractable hemorrhage who will need surgery. Delay in making this decision can be catastrophic. The successful use of the inflated stomach balloon of a Sengstaken-Blakemore tube as a therapy for obstetric hemorrhage has been reported previously. Using the insertion of the Sengstaken-Blakemore tube as a diagnostic test has not been reported. An inflated Sengstaken-Blakemore balloon catheter creates tamponade and identifies those who will or will not need surgery. This is the basis for the "tamponade test." We evaluated the tamponade test in the management of women with massive postpartum hemorrhage. METHODS: In this prospective study, 16 cases of intractable postpartum hemorrhage were managed by the tamponade test. All 16 women had persistent bleeding despite the maximal and optimal application of conservative measures. Their condition deteriorated, such that surgical intervention was considered mandatory. It was at this predefined end point that the tamponade test was applied. RESULTS: Fourteen (87.5%) had a positive tamponade test result and therefore did not require surgery. Two (12.5%) had a negative test result and underwent laparotomy. CONCLUSION: This diagnostic test rapidly identifies those patients with postpartum hemorrhage who will require a laparotomy. Even when results are positive, life-threatening hemorrhage is arrested and time is also allowed to correct any consumptive coagulopathy.

Adult↗
PubMed2003

Randomized comparison of photodynamic therapy with topical 5-fluorouracil in Bowen's disease.

BACKGROUND: Bowen's disease (BD; intraepithelial squamous cell carcinoma) is therapeutically challenging because lesions, which may be multiple, are frequently located at sites that heal poorly. There is a small risk of progression to invasive carcinoma. Photodynamic therapy (PDT) is an effective treatment for certain non melanoma skin cancers, but comparison studies with other, better-established therapies are limited. OBJECTIVES: To compare the efficacy and tolerability of PDT and topical 5-fluorouracil (5-FU) in BD. METHODS: Forty patients from two centres were randomized to either topical PDT or 5-FU. The PDT group was treated with 20% 5-aminolaevulinic acid (ALA) applied 4 h before illumination with 100 J cm-2 narrowband red light (630 +/- 15 nm). 5-FU was applied to lesions for 4 weeks. A repeat treatment cycle was performed after 6 weeks if required. Results Twenty-nine of 33 (88%) lesions treated with PDT initially responded completely, compared with 22 of 33 (67%) after 5-FU. After 12 months, two recurrences in the PDT group and six in the 5-FU group reduced complete clinical clearance rates to 82% and 48%, respectively. PDT was significantly more effective (P = 0.006, odds ratio 4.78, 95% confidence interval 1.56-14.62). In the 5-FU group, severe eczematous reactions developed around seven lesions, ulceration in three and erosions in two. No such reactions occurred following PDT. There was no difference in overall pain experienced during each therapy. CONCLUSIONS: Topical ALA-PDT is more effective than topical 5-FU in the treatment of BD, with fewer adverse events. ALA-PDT should be considered one of the first-line therapeutic options for BD.

Administration, Topical↗
PubMed2002

Integrating cost-effectiveness evidence into clinical practice guidelines in Australia for acute myocardial infarction.

A teaching hospital is working with the Victorian State Government and universities, integrating cost-effectiveness evidence into clinical practice guidelines (CPGs), protocols and pathways for respiratory and cardiology interventions. Acute myocardial infarction (AMI) findings are reported. Results will stimulate cost-effective practice and inform medical associations, federal and state governments and international organisations developing CPGs. Published CPGs by the American College of Cardiology/American Heart Foundation for AMI in 1999 are reviewed by a large interdisciplinary hospital-based committee given cost-effectiveness evidence. Levels of evidence criteria rating on methodological rigor for effectiveness and costs are applied. National Health and Medical Research Council (NHMRC) grades of recommendation criteria for combinations of relative effectiveness versus relative costs and cut-off points are used. Extrapolating results between countries was addressed by applying the OECD's health purchasing power parity series. Recommendations for revisions to United States guidelines and for local application are formulated. United States Guidelines require updating: Regarding angioplasty, percutaneous transluminal coronary angioplasty (PTCA) is cost-effective for men aged 60 years relative to recombinant tissue plasminogen activator (tPA), with additional cost per life year saved of 274 ecu. PTCA with discharge after 3 days is cost-effective in low-risk AMI. Regarding GP IIb/IIIa drugs, Abciximab during intervention incurred equal mean hospital costs for placebo, abciximab bolus, and abciximab bolus+infusion with incremental 6-month cost for the latter treatment costing 293 US dollars per patient. Agent recouped almost all initial therapy costs with significant benefits. Incremental cost of abciximab per event prevented is 3,258 US dollars. Tirofiban was compared to placebo after high-risk angioplasty for AMI or unstable angina. Tirofiban decreased the rate of hospital deaths, myocardial infarction, revascularisation at 2 days by 36% relative to placebo (8% vs. 12%) without increased cost. Clinical benefits were similar at 30 days. Tirofiban+heparin+aspirin was compared to heparin+aspirin. Tirofiban arm resulted in net savings of 33,418 ecu per 100 patients for the first 7 days of treatment. Regarding thrombolytics, tPA is more cost-effective than streptokinase. Incremental costs for each life saved when streptokinase is substituted by recombinant tissue plasminogen are 31%, 45%, 97% higher in Germany, Italy and the United States than in the United Kingdom. Regarding anticoagulants, enoxaparin is a promising alternative to unfractionated heparin for hospitalised patients with non-Q-wave myocardial infarction or unstable angina, saving 1,485 Canadian dollars per patient over 12 months with 10% reduction in 1 year risk of death, myocardial infarction or recurrent angina. Regarding antiarrhymics, the cost-effectiveness of no amiodarone, amiodarone for patients with depressed heart rate variability (DHRV), and amiodarone for patients with DHRV plus positive programmed ventricular stimulation (PPVS) for high-risk post-AMI was investigated. Amiodarone for DHRV+PPVS patients was dominated by a blend of the two alternatives. Compared to no amiodarone, the incremental cost-effectiveness of amiodarone for DHRV patients was 39,422 US dollars per quality adjusted life year gained. Amiodarone for DHRV is the most appropriate. Other CPG updates concern serum markers, for example, cardiac troponin I assay (c-Tnl), cost advantages of ad hoc angioplasty and secondary prevention through antioxidants and pravastatin. Australian costs are reported later in the paper.

Journal Article↗
PubMed2002

Cholangiocarcinoma in primary sclerosing cholangitis: risk factors and clinical presentation.

BACKGROUND: Primary sclerosing cholangitis (PSC) confers a high risk of cholangiocarcinoma (CC) development. Since patients at risk of CC may be selected for early liver transplantation, it is a challenge to identify any predisposing factors. We compared the presentation and natural history of a large number of PSC patients with and without later CC development to identify features associated with risk of CC. METHODS: Clinical and laboratory data from presentation and follow-up were collected from 394 PSC patients from five European countries. The cohort included 48 (12.2%) patients with CC. RESULTS: CC was diagnosed within the first year after diagnosis of PSC in 24 (50%) cases and in 13 (27%) patients at intended liver transplantation. Jaundice, pruritus, abdominal pain and fatigue were significantly more frequent at diagnosis of PSC in the group that developed CC, but not after exclusion of cases diagnosed within the first year. Inflammatory bowel disease was diagnosed at least 1 year before PSC more often among patients with CC development than among those without (90% and 65%, respectively: P = 0.001). The duration of inflammatory bowel disease before diagnosis of PSC was significantly longer in patients who developed CC than in the remaining group (17.4 years and 9.0 years, respectively: P=0.009 in multivariate analysis). CONCLUSIONS: A high proportion of CC cases is diagnosed within the first year after diagnosis of PSC. A long history of inflammatory bowel disease is a risk factor for CC development.

Adult↗
PubMed2001

Comparison of PDE 4 inhibitors, rolipram and SB 207499 (ariflo), in a rat model of pulmonary neutrophilia.

Using a rat model of lipopolysaccharide (LPS)-induced pulmonary inflammation, the antiinflammatory activity of SB 207499 was evaluated and compared to that of the prototypic type-4 phosphodiesterase (PDE4) inhibitor, rolipram. In dose-response experiments, we found that rats exposed to 10 microg or 100 microg of intratracheal (it) LPS developed a prominent pulmonary inflammation, due to a significant increase in the number of recoverable bronchoalveolar lavage neutrophils. The pulmonary neutrophilia, provoked by the challenge of 10 microg LPS/rat, was significant at 2 h, peaked by 16 h, declined thereafter but remained elevated for up to 48 h. Additionally, the exposure of rats to 10 microg LPS caused the local pulmonary production of TNF- alpha. In contrast to the cellular influx, TNF- alpha production peaked at 2 h and rapidly declined to negligible levels by 8 h. While low levels were detected, the levels of IL-1 beta in bronchoalveolar lavage did not significantly differ from saline challenged animals. Rats pretreated with rolipram or SB 207499, displayed dose-dependent inhibition of the LPS-induced pulmonary inflammation. Nevertheless, the pulmonary production of TNF- alpha and IL-1 beta was unaffected by either SB 207499 or rolipram. When provoked with the 10 microg dose of LPS, adrenalectomized rats produced a similar 24 h induction of pulmonary neutrophilia. Pretreatment of adrenalectomized rats with the PDE4 inhibitors showed similar inhibitory results to those obtained in normal rats. In summary, we have shown, using a rat model of LPS-induced pulmonary neutrophilic inflammation, that the inhibitory activities of rolipram or SB207499 are not linked to the production of TNF- alpha or the inhibition of IL-1 beta, and occur independently of endogenous catecholamine or corticosteroid release.

Adrenalectomy↗
PubMed2001

Effect of HLA class II genotype on T helper lymphocyte responses and viral control in hepatitis C virus infection.

Hepatitis C virus (HCV) infection is very common worldwide, but has a broad range of outcomes. A minority of patients are able to clear infection spontaneously, and this is thought to be due to the emergence and maintenance of effective cell-mediated immunity, particularly CD4+ T lymphocyte responses. Furthermore, genetic studies have indicated that HLA class II genotype strongly influences the outcome of infection. We have therefore investigated the influence of the protective HLA class II haplotype (DQB1*0301, which is in tight linkage disequilibrium with DRB1*1101) on the CD4+ T lymphocyte responses to HCV. We observe a strong association between this genotype and maintenance of a multispecific CD4+ T helper response. The effect on T helper responses was also maintained after combination interferon-alpha/ribavirin therapy, although the latter influenced the pattern of viral antigens to which patients responded. This is the first disease in which an association of HLA genotype with clinical outcome has been linked to an alteration of the immunological phenotype. The selection of protective peptides in those with the favourable HLA class II genotype may point in the direction of suitable vaccine candidates.

Adult↗
PubMed2001

Types of patients in a psychiatric intensive care unit.

OBJECTIVE: This paper reports the findings of a descriptive study of a patient population over a three-month period on an eight bed psychiatric intensive care unit (PICU) in Western Australia. The report provides a quantitative insight into the profile of patients in PICUs. It provides information on patients' diagnoses, presenting signs, symptoms and/or behaviours, legal codes assigned to patients, treatment interventions and management. METHOD: Data were collected prospectively from August to October 1999. A total of 122 patients were admitted to the PICU during the review period. Data were entered into an Access program then exported to SPSS (Version 9 for Windows) for analysis and frequency distributions were obtained. RESULTS: The results confirmed that the majority of patients admitted to the PICU were assessed as a high level of risk or needed containment. This finding is in line with the admission criteria developed by staff working in the PICU. It also supports the view that staff working in these units require expertise and confidence to communicate with and manage potentially aggressive and highly aroused patients. CONCLUSION: This study demonstrates the importance of ongoing evaluations of patient populations in promoting best practice initiatives in psychiatric care.

Adult↗
PubMed2001

Aetiopathogenesis of primary sclerosing cholangitis.

The aetiology and pathogenesis of PSC have not yet been clearly defined. The hypothesis that PSC is an immune mediated disease is supported by associations with HLA haplotypes, the presence of autoantibodies, increased levels of total serum immunoglobulins and the association with other autoimmune diseases. PSC does not, however, have many of the characteristics of classical autoimmunity, particularly the usual female preponderance of disease and lack of a good response to immunosuppression. Non-immune mechanisms such as bacterial infection, ischaemia and toxicity are also clearly important in the development of the disease and these factors may trigger peribiliary inflammation and cytokine-induced hepatic fibrosis. PSC may be triggered in genetically susceptible individuals by toxic or infectious agents gaining access to the liver via a diseased and permeable colon.

Bacterial Infections↗
PubMed2001

Mapping MHC-encoded susceptibility and resistance in primary sclerosing cholangitis: the role of MICA polymorphism.

BACKGROUND & AIMS: Recent studies suggest that major histocompatibility complex-encoded susceptibility to primary sclerosing cholangitis (PSC) maps to the HLA B-TNFA region on chromosome 6p21.3. METHODS: The present study uses a standard polymerase chain reaction protocol to investigate the 16 common alleles of the MICA locus as candidates in 2 patient populations (King's College Hospital, London, and John Radcliffe Hospital, Oxford). RESULTS: The MICA*002 allele was found in 4 of 62 (6.4%) patients and none of 50 patients vs. 41 of 118 (35%) controls (pc = 0.00018, odds ratio [OR] = 0.12, and P = 0.0000016, OR = 0.0, respectively). Overall, the MICA*008 allele was more common in PSC (gene frequency 66% vs. 48% of controls, P = 0.0023, OR = 2.11). However, unlike MICA*002 in which the difference was a result of the absence of MICA*002 heterozygotes, the MICA*008 association may be caused by an increased frequency of MICA*008 homozygosity in patients (58% vs. 22%, pc = 0.000015, OR = 5.01 and 58% vs. 22%, P = 0.0000056, OR = 4.51, respectively). Though MICA*008 is found on the ancestral 8.1 haplotype, stratification analysis indicates that this association is independent of B8 and other HLA haplotypes associated with PSC. CONCLUSIONS: The MICA*002 allele has a strong dominant effect in reducing the risk of PSC, whereas the increased risk of disease associated with MICA*008 may be a recessive effect requiring 2 copies of the MICA*008 allele.

Adolescent↗
PubMed2001

The HLA-DR3,DQ2 heterozygous genotype is associated with an accelerated progression of primary sclerosing cholangitis.

BACKGROUND: An improvement of prognostic models in primary sclerosing cholangitis (PSC) is needed. In particular, inclusion of prognostic markers that are independent of the disease stage would be advantageous. We investigated whether HLA class II genes associated with PSC are also related to disease progression. METHODS: The study included 265 PSC patients from five European countries with a median follow-up of 9.1 years. The end-points were death (n = 38) or liver transplantation (n = 52). Thirty patients developed cholangiocarcinoma during follow-up. RESULTS: The DRB1*03,DQA1*0501, DQB1*02 (i.e. DR3,DQ2) heterozygous genotype was associated with an increased risk of death or liver transplantation (hazard ratio = 1.63; 95% confidence interval (CI) = 1.06-2.52). The presence of a DQ6 encoding haplotype (DQB1*0603 or DQB1*0602) in DR3,DQ2 negative individuals was associated with a reduced risk of death or liver transplantation (hazard ratio = 0.57; 95% CI = 0.36-0.88). There was a trend towards an increased risk of developing cholangiocarcinoma among DR4,DQ8 positive patients, but this did not reach significance (odds ratio = 2.27; 95% CI = 0.78-6.62). CONCLUSION: The DR3,DQ2 heterozygous genotype is associated with a more rapid progression of PSC, whereas HLA-DQ6 is associated with a retarded disease progression. It is possible that the DR4,DQ8 haplotype is related to cholangiocarcinoma development.

Adolescent↗
PubMed2001

Combination therapy with interferon-alpha and ribavirin for hepatitis C: practical treatment issues.

Combination therapy with ribavirin and interferon (IFN)-alpha for 6 to 12 months is currently the treatment of choice for chronic hepatitis C infection. The overall sustained response rate to treatment, defined as loss of hepatitis C virus (HCV) from serum 6 months after completion of treatment, is 40%. The indications for treatment are serum HCV RNA positivity, abnormal serum transaminases and the presence of portal fibrosis and/or moderate/severe inflammation. Response rates are lower in genotype 1 than in genotype 2 or 3 and in the presence of a high viral load. Anaemia is the most common adverse event and is due to ribavirin; neuropsychiatric adverse effects due to IFNalpha lead to premature cessation of therapy in 10 to 20% of patients. The current recommended dose of interferon is 3MU given subcutaneously 3 times a week. However, it is likely that longer-acting pegylated interferons, which may be more effective and can be administered once weekly, will in the future replace currently used IFNalpha.

Antiviral Agents↗