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J Mitchell

Publications and source records attributed to J Mitchell.

At least 19 recordsLinked to original sources
PubMed2006

A unilateral NMR magnet for sub-structure analysis in the built environment: the Surface GARField.

A new, portable NMR magnet with a tailored magnetic field profile and a complementary radio frequency sensor have been designed and constructed for the purpose of probing in situ the sub-surface porosity of cement based materials in the built environment. The magnet is a one sided device akin to a large NMR-MOUSE with the additional design specification of planes of constant field strength /B0/ parallel to the surface. There is a strong gradient G in the field strength perpendicular to these planes. As with earlier GARField magnets, the ratio G//:B0/ is a system constant although the method of achieving this condition is substantially different. The new magnet as constructed is able to detect signals 50mm (1H NMR at 3.2 MHz) away from the surface of the magnet and can profile the surface layers of large samples to a depth of 35-40 mm by moving the magnet, and hence the resonant plane of the polarising field, relative to the sample surface. The matching radio frequency excitation/detector coil has been designed to complement the static magnetic field such that the polarising B0 and sensing B1 fields are, in principal, everywhere orthogonal. Preliminary spatially resolved measurements are presented of cement based materials, including two-dimensional T1-T2 relaxation correlation spectra.

Construction Materials↗
PubMed2006

Sustained virological response rates and durability of the response to interferon-based therapies in hepatitis C patients treated in the clinical setting.

International controlled trials have demonstrated increasing sustained virological response (SVR) rates to interferon-based therapies in hepatitis-C-treated patients. Response rates of 6-20% in the era of interferon monotherapy are compared with 42-82% with pegylated interferon plus ribavirin. The virological durability of the SVR is unknown and the optimal follow-up for these patients is unclear. The aim of our study was to determine SVR rates and the durability of the response to interferon-based therapies in the clinical setting. From our database of 1540 hepatitis C patients, 344 treatment courses of at least 12 weeks duration were identified, including interferon monotherapy (175 patients), interferon plus ribavirin (96 patients) and peginterferon plus ribavirin (73 patients). Interferon monotherapy was associated with an SVR rate of 5% in 103 genotype 1 patients and 25% in 72 genotype 2/3 patients. Response rates were higher (P < 0.001) with interferon plus ribavirin-41% in 34 genotype 1 patients and 73% in 62 genotype 2/3 patients-and with peginterferon plus ribavirin-47% in 47 genotype 1 patients and 79% in 26 genotype 2/3 patients. Of 147 patients with an SVR, 146 (>99%) remained hepatitis C virus PCR negative during a mean 2.3 years (range 0.3-10.3) of follow-up. In conclusion, with advances in therapies, we are achieving higher response rates in hepatitis C patients treated in the clinical setting. We can now expect an SVR in over half of the treated patients. Importantly, the response is durable and medium and long-term follow-up of these patients are of low yield and largely unnecessary.

Adolescent↗
PubMed2006

Effect of age related macular degeneration on the Eger macular stressometer photostress recovery time.

AIM: To assess the repeatability of Eger macular stressometer (EMS) measures of photostress recovery and determine their association with other measures of visual function. METHODS: EMS photostress recovery time was measured in 90 patients with bilateral exudative age related macular degeneration (AMD), 19 with bilateral atrophic AMD and 47 with both forms of the condition (mean age 79 (SD 13) years). Measurements were made on two occasions separated by 1 year. Intrasession repeatability was assessed by repeating the measures after a 10 minute recovery period at the first visit. Distance visual acuity was measured with a logMAR chart, near visual acuity with a MNRead chart at 25 cm, contrast sensitivity with a Pelli-Robson chart, and the presence of central visual disturbance assessed with an Amsler grid. A questionnaire was used to assess self reported difficulties with glare recovery. RESULTS: The average EMS recovery time was 11.0 (SD 8.9) seconds, decreasing by 1.6 (5.2) seconds on repeated measurement (p<0.05). EMS photostress recovery was not correlated with visual function measures or subjective difficulties with lights (p>0.05). EMS photostress recovery time did not predict those whose vision decreased over the following year compared with those among whom it remained stable. CONCLUSIONS: The EMS test is not a useful tool in determining the severity or progression of AMD.

Adaptation, Ocular↗
PubMed2005

Ovarian cancer presenting as chest wall subcutaneous nodule: a case report and a literature review.

BACKGROUND: Distant metastasis from primary epithelial ovarian carcinoma is commonly found as nodal and intraperitoneal spread, spread via haematogenous routes or transcoelomic spread. Ovarian cancer presents in different ways, but common presentations include abdominal pain, distention or ascites due to metastatic involvement of peritoneal cavity. Most tumour present at advanced stage and distant metastases to common and uncommon sites are found in patients who have undergone treatment for primary ovarian cancer. Subcutaneous metastatic nodules from primary ovarian cancer are rarely found in advanced disease. We describe a case of asymptomatic ovarian carcinoma presenting as a chest wall nodule. CASE: An unusual case of primary ovarian carcinoma presenting as asymptomatic chest wall subcutaneous nodules that subsequently were diagnosed as metastatic lesions. CONCLUSION: An unusual case of ovarian carcinoma where the patient was totally asymptomatic and referred with two tiny subcutaneous nodules. Therefore, lumps of recent onset, although asymptomatic, should either have fine needle aspiration cytology or excision biopsy.

Adenocarcinoma↗
PubMed2005

Recoil polarization for delta excitation in pion electroproduction.

We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W = 1.23 GeV at Q(2) = 1.0 (GeV/c)(2), obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S(1+)/M(1+)) = -(6.84 +/- 0.15)% and Re (E(1+)/M(1+)) = -(2.91 +/- 0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ll(pi) < or = 1 truncation.

Journal Article↗
PubMed2005

Surface relaxation and chemical exchange in hydrating cement pastes: a two-dimensional NMR relaxation study.

We report the first nuclear magnetic resonance (NMR) two-dimensional correlation T(1) - T(2) and T(2) - T(2) measurements of hydrating cement pastes. A small but distinct cross peak in the two-dimensional relaxation spectrum provides the first direct evidence of chemical exchange of water between gel and capillary pores occurring over the first 14 days of hydration. A correlation of features along the line T(1) = 4T(2) provides strong supportive evidence for the surface diffusion model of (1)H nuclear spin relaxation in cements and for a multimodal discrete pore size distribution. Differences in detail of the results are reported for white cement paste and white cement paste with added silica fume. Both the method and the theory presented can be applied more widely to other high surface area materials with other reactive surface areas.

Journal Article↗
PubMed2005

Growth in children with Helicobacter pylori infection and dyspepsia.

AIMS: To compare the height, weight, and body mass index (BMI) of children presenting with dyspeptic symptoms and Helicobacter pylori infection, to those with dyspepsia but without the infection. METHODS: A retrospective chart review of 257 children was performed. 13C urea breath test was performed to detect H pylori infection; weight and height were recorded and BMI was calculated. Weight, height, and BMI SD scores were determined using the 1990 UK normative data. The Index of Multiple Deprivation 2004 (IMD 2004) scores, which measure deprivation at small area level, were calculated from the patients' postcodes. RESULTS: Ninety seven of the 257 children were H pylori positive. The mean age at diagnosis and presenting symptoms of H pylori positive and negative patients were similar. The mean IMD 2004 scores for children with H pylori infection were significantly higher compared to H pylori negative patients, suggesting that children with the infection came from relatively more deprived areas. The mean weight and height SD score were significantly lower for children with H pylori infection compared to those without. However, this difference was no longer significant after adjusting for socioeconomic deprivation and ethnic differences between the groups. CONCLUSION: Children with dyspepsia and H pylori infection were shorter and lighter than patients with similar symptoms but no infection. The differences in anthropometry may be due to socioeconomic and ethnic factors rather than H pylori infection.

Adolescent↗
PubMed2005

Quasielastic 3He(e,e'p)2H reaction at Q2 = 1.5 GeV2 for recoil momenta up to 1 GeV/c.

We have studied the quasielastic 3He(e,e(')p)2H reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e(')p)2H cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.

Journal Article↗
PubMed2005

Measurement of the 3He(e,e'p)pn reaction at high missing energies and momenta.

Results of the Jefferson Lab Hall A quasielastic 3He(e,e'p)pn measurements are presented. These measurements were performed at fixed transferred momentum and energy, q=1502 MeV/c and omega=840 MeV, respectively, for missing momenta p(m) up to 1 GeV/c and missing energies in the continuum region, up to pion threshold; this kinematic coverage is much more extensive than that of any previous experiment. The cross section data are presented along with the effective momentum density distribution and compared to theoretical models.

Journal Article↗
PubMed2005

Natural dissemination of Bacillus anthracis spores in northern Canada.

Soil samples were collected from around fresh and year-old bison carcasses and areas not associated with known carcasses in Wood Buffalo National Park during an active anthrax outbreak in the summer of 2001. Sample selection with a grid provided the most complete coverage of a site. Soil samples were screened for viable Bacillus anthracis spores via selective culture, phenotypic analysis, and PCR. Bacillus anthracis spores were isolated from 28.4% of the samples. The highest concentrations of B. anthracis spores were found directly adjacent to fresh carcasses and invariably corresponded to locations where the soil had been saturated with body fluids escaping the carcass through either natural body orifices or holes torn by scavengers. The majority of positive samples were found within 2 m of both year-old and fresh carcasses and probably originated from scavengers churning up and spreading the body fluid-saturated soil as they fed. Trails of lesser contamination radiating from the carcasses probably resulted from spore dissemination through adhesion to scavengers and through larger scavengers dragging away disarticulated limbs. Comparison of samples from minimally scavenged and fully necropsied carcass sites revealed no statistically significant difference in the level of B. anthracis spore contamination. Therefore, the immediate area around a suspected anthrax carcass should be considered substantially contaminated regardless of the condition of the carcass.

Animals↗
PubMed2004

Angular distributions for (3,4)(Lambda)H bound states in the (3,4)He(e,e(')K+) reaction.

The (3,4)(Lambda)H and (4)(Lambda)H hypernuclear bound states have been observed for the first time in kaon electroproduction on (3,4)He targets. The production cross sections have been determined at Q(2)=0.35 GeV2 and W=1.91 GeV. For either hypernucleus the nuclear form factor is determined by comparing the angular distribution of the (3,4)He(e,e(')K+)(3,4)(Lambda)H processes to the elementary cross section 1H(e,e K+)Lambda on the free proton, measured during the same experiment.

Journal Article↗
PubMed2004

Neonatal diabetes, with hypoplastic pancreas, intestinal atresia and gall bladder hypoplasia: search for the aetiology of a new autosomal recessive syndrome.

AIMS/HYPOTHESIS: Neonatal diabetes is a rare disease with several identified molecular aetiologies. Despite associations with other malformations, neonatal diabetes with intestinal and biliary anomalies has not been described. The current study aims to describe a new syndrome, and to examine a possible link with one of three genes known to cause neonatal diabetes. METHODS: Five clinical cases are described. Immunohistochemical staining for pancreatic islet hormones was performed on three of the infants. DNA from one infant was analysed for abnormalities of the PLAGL-1 (ZAC), glucokinase and PDX-1 (IPF-1) genes. RESULTS: Five infants (two sibling pairs from two families, and an isolated case) presented with neonatal diabetes, hypoplastic or annular pancreas, jejunal atresia, duodenal atresia and gall bladder aplasia or hypoaplasia. One sibling pair was born to consanguineous parents. One patient with a milder form is surviving free of insulin. Four children died in the first year of life despite aggressive medical management. Pancreatic immunohistochemistry revealed few scattered chromogranin-A-positive cell clusters but complete absence of insulin, glucagon and somatostatin. Exocrine histology was variable. In one case from the consanguineous family, molecular analysis showed no duplication or uniparental isodisomy of PLAGL-1 at 6q24, no contiguous gene deletion involving the glucokinase gene, and no mutation in the coding sequences or splice sites of PDX-1. CONCLUSIONS/INTERPRETATION: This combination of multiple congenital abnormalities has not been previously described and probably represents a new autosomal recessive syndrome involving a genetic abnormality that interferes with normal islet development and whose aetiology is as yet unknown.

Abnormalities, Multiple↗
PubMed2004

Measurement of the generalized forward spin polarizabilities of the neutron.

The generalized forward spin polarizabilities gamma(0) and delta(LT) of the neutron have been extracted for the first time in a Q2 range from 0.1 to 0.9 GeV2. Since gamma(0) is sensitive to nucleon resonances and delta(LT) is insensitive to the Delta resonance, it is expected that the pair of forward spin polarizabilities should provide benchmark tests of the current understanding of the chiral dynamics of QCD. The new results on delta(LT) show significant disagreement with chiral perturbation theory calculations, while the data for gamma(0) at low Q2 are in good agreement with a next-to-leading-order relativistic baryon chiral perturbation theory calculation. The data show good agreement with the phenomenological MAID model.

Journal Article↗
PubMed2004

A 13-week oral toxicity study of senna in the rat with an 8-week recovery period.

Senna was administered by gavage to Sprague Dawley rats once daily at dose levels of 0, 100, 300, 750 or 1500 mg/kg for up to 13 consecutive weeks followed by an 8-week recovery period for selected animals. Dose- and treatment-related clinical signs included abnormal feces, which were seen to varying degrees from animals at 300 mg/kg per day and more. Animals receiving 750 or 1500 mg/kg per day had significantly reduced body weight gain (males only) and, related to the laxative properties of senna, increased water consumption and notable changes in electrolytes in both serum and urine. At both the terminal and recovery phase necropsy, an increase in absolute and relative kidney weights was seen for male and female animals receiving 750 and/or 1500 mg/kg per day. A dark discoloration of the kidneys was observed at necropsy along with histopathological changes in the kidneys (slight to moderate tubular basophilia and pigment deposits) at 300 mg/kg and above. However, there were no indications in laboratory parameters of any renal dysfunction. In addition, for all treated groups, minimal to slight hyperplasia was recorded in the forestomach and large intestine. Following 8 weeks of recovery, with the exception of the brown pigment in the kidneys, there were no histopathological abnormalities. Thus, the biochemical and morphological changes seen following 13 weeks of treatment of senna significantly reversed following 8 weeks of recovery.

Administration, Oral↗
PubMed2004

Binary liquid mixtures in porous solids.

The technique of nuclear magnetic resonance cryoporometry has been used to study the behavior of binary liquid mixtures of water and decane in porous sol-gel silicas. It was observed that the water preferentially adsorbed onto the silica surface and so was able to displace the decane from the pores.

Journal Article↗
PubMed2004

Measurement of the electric form factor of the neutron at Q2=0.5 and 1.0 GeV2/c2.

The electric form factor of the neutron was determined from measurements of the d-->(e-->,e'n)p reaction for quasielastic kinematics. Polarized electrons were scattered off a polarized deuterated ammonia (15ND3) target in which the deuteron polarization was perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle detector. We find G(n)(E)=0.0526+/-0.0033(stat)+/-0.0026(sys) and 0.0454+/-0.0054+/-0.0037 at Q(2)=0.5 and 1.0 (GeV/c)(2), respectively.

Journal Article↗