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John King

Publications and source records attributed to John King.

17 recordsLinked to original sources
PubMed2006

FEM calculation of an acoustic field in a sonochemical reactor.

The spatial distribution of the acoustic amplitude in a sonochemical reactor has been numerically calculated using the finite element method (FEM). In the FEM program, the acoustic field in a sonochemical reactor is coupled with the vibration of the reactor's wall. The present calculations have revealed that the thin (thick) glass or stainless steel wall is nearly a free (rigid) boundary and that the glass wall is freer than the stainless steel wall. The influence of the attenuation coefficient of ultrasound on the acoustic field has also been studied in order to see the effect of bubbles on the acoustic field. As the attenuation coefficient increases, the vibration amplitude of the reactor's wall becomes smaller and the acoustic emission from the vibrating wall becomes weaker. The qualitative feature of the spatial pattern of sonochemiluminescence from an aqueous luminol solution has been reproduced by the calculation when the attenuation coefficient is in the range of 0.5-5m(-1). When the attenuation coefficient is less than about 0.05 m(-1), the standing wave pattern of an acoustic field in the liquid is very complex due to the acoustic emission from the vibrating wall. The present calculations have also revealed that some stripes of pressure antinodes have also been disconnected when the radius of the transducer is much smaller than the side length of the vibrating plate. The dependence of the acoustic field on the liquid height is also discussed.

Journal Article↗
PubMed2006

The Cenozoic palaeoenvironment of the Arctic Ocean.

The history of the Arctic Ocean during the Cenozoic era (0-65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from >400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm 'greenhouse' world, during the late Palaeocene and early Eocene epochs, to a colder 'icehouse' world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent approximately 14 Myr, we find sedimentation rates of 1-2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (approximately 3.2 Myr ago) and East Antarctic ice (approximately 14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (approximately 45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at approximately 49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (approximately 55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change.

Animals↗
PubMed2006

Wound-induced terpene synthase gene expression in Sitka spruce that exhibit resistance or susceptibility to attack by the white pine weevil.

We analyzed the expression pattern of various terpene synthase (TPS) genes in response to a wounding injury applied to the apical leader of Sitka spruce (Picea sitchensis Bong. Carr.) genotypes known to be resistant (R) or susceptible (S) to white pine weevil (Pissodes strobi Peck.) attack. The purpose was to test if differences in constitutive or wound-induced TPS expression can be associated with established weevil resistance. All wounding treatments were conducted on 9-year-old R and S trees growing under natural field conditions within the range of variation for weevil R and S genotypes. Representative cDNAs of the monoterpene synthase (mono-TPS), sesquiterpene synthase (sesqui-TPS), and diterpene synthase (di-TPS) classes were isolated from Sitka spruce to assess TPS transcript levels. Based on amino acid sequence similarity, the cDNAs resemble Norway spruce (Picea abies) (-)-linalool synthase (mono-TPS; PsTPS-Linl) and levopimaradiene/abietadiene synthase (di-TPS; PsTPS-LASl), and grand fir (Abies grandis) delta-selinene synthase (sesqui-TPS; PsTPS-Sell). One other mono-TPS was functionally identified as (-)-limonene synthase (PsTPS-Lim). No significant difference in constitutive expression levels for these TPSs was detected between R and S trees. However, over a postwounding period of 16 d, only R trees exhibited significant transcript accumulation for the mono- and sesqui-TPS tested. Both R and S trees exhibited a significant accumulation of PsTPS-LASl transcripts. An assessment of traumatic resin duct formation in wounded leaders showed that both R and S trees responded by forming traumatic resin ducts; however, the magnitude of this response was significantly greater in R trees. Collectively, our data imply that the induced resinosis response is an important aspect of defense in weevil R Sitka spruce trees growing under natural conditions.

Alkyl and Aryl Transferases↗
PubMed2006

Health policy and the delivery of evidence-based wound care using regional wound teams.

As clinicians practicing wound management in all three sectors of the healthcare system, the authors have articulated specific issues relating to wound management. There is a lack of awareness of the extent of the problem. Best practice guidelines have been developed, however, their adoption and transfer into practice have been inconsistent. Basic education in the field is minimal or absent across all disciplines. Institutions and agencies lack the infrastructure and financial resources to support optimal healthcare delivery in wound prevention and management. As a result, there are significant problems and inconsistencies in access to wound care across Ontario. This paper reviews the issues and background as related to pressure ulcer, diabetic foot ulcer and venous leg ulcer. Finally, the authors make specific health policy recommendations regarding the implementation of regional wound care teams.

Evidence-Based Medicine↗
PubMed2006

Impaired allocentric spatial memory underlying topographical disorientation.

The cognitive processes supporting spatial navigation are considered in the context of a patient (CF) with possible very early Alzheimer's disease who presents with topographical disorientation. Her verbal memory and her recognition memory for unknown buildings, landmarks and outdoor scenes was intact, although she showed an impairment in face processing. By contrast, her navigational ability, quantitatively assessed within a small virtual reality (VR) town, was significantly impaired. Interestingly, she showed a selective impairment in a VR object-location memory test whenever her viewpoint was shifted between presentation and test, but not when tested from the same viewpoint. We suggest that a specific impairment in locating objects relative to the environment rather than relative to the perceived viewpoint (i.e. allocentric rather than egocentric spatial memory) underlies her topographical disorientation. We discuss the likely neural bases of this deficit in the light of related studies in humans and animals, focusing on the hippocampus and related areas. The specificity of our test indicates a new way of assessing topographical disorientation, with possible application to the assessment of progressive dementias such as Alzheimer's disease.

Activities of Daily Living↗
PubMed2003

Posterior segment complications in patients with hepatitis C treated with interferon and ribavirin.

PURPOSE: To determine the incidence and type of posterior segment complications associated with the use of interferon alpha 2b and ribavirin in patients with chronic hepatitis C. DESIGN: A prospective noncomparative case series. PARTICIPANTS: Forty-two patients (84 eyes). METHODS: Patients with chronic hepatitis C were evaluated for ocular changes while being treated with interferon alpha 2b and ribavirin. Patients were followed with sequential ocular examinations for 4 to 20 months. MAIN OUTCOME MEASURES: Occurrence of posterior segment complications while on interferon and ribavirin therapy. RESULTS: Twenty-seven patients developed retinopathy. The retinopathy consisted of single-to-multiple cotton-wool spots and retinal hemorrhage and was transient in all cases. An additional patient (age 46) presented with asymptomatic disc edema and hemorrhage. One other individual developed a symptomatic permanent monocular visual field defect. Therapy was discontinued in three patients because of severe posterior segment pathology. CONCLUSIONS: Our study demonstrated that a high incidence of retinopathy is associated with the treatment of hepatitis C using interferon and ribavirin, but that this form of retinopathy is relatively benign. Regular ophthalmic monitoring should be performed in patients undergoing this treatment.

Adult↗
PubMed2003

Young adults admitted for asthma: does gender influence outcomes?

OBJECTIVE: To assess any outcome differences between young men and women who are admitted for asthma. METHODS: We conducted a retrospective cohort study based on hospitalizations. An inclusion criterion was admission for asthma between January 1, 1998 and July 1, 2001. Exclusion criteria included age >45, chronic obstructive pulmonary disease (COPD), and emphysema. Data were collected on 10 potential confounding variables. Four outcome variables were assessed, including length of stay, intensive care unit (ICU) length of stay, mortality, and respiratory failure. RESULTS: Patients admitted for asthma were significantly more likely to be female (374 females vs. 106 males, p <0.05). There was no difference between the genders comparing month of admission. The women were significantly older, with more Medicaid insured, and more anxiety/depression (p <0.05). There was no difference between the genders for obesity, race, tobacco history, gastroesophageal reflux disease (GERD), hypertension, diabetes, and pneumonia. There was no reported mortality. Using regression analysis, there was no difference between the genders for length of stay (odds ratio [OR] = 1.06, 95% confidence interval [CI] 0.97-1.17) and respiratory failure (OR = 1.58, 95% CI 0.53-4.76). Men stayed significantly longer in the ICU (OR = 1.18, 95% CI 1.01-1.38). CONCLUSIONS: Patients admitted with asthma are significantly more likely to be female. Males stay significantly longer in the ICU. There is no difference between the genders for length of stay and respiratory failure. There was no reported mortality for either gender.

Adolescent↗
PubMed2003

Modelling cereal root systems for water and nitrogen capture: towards an economic optimum.

A quantitative model of wheat root systems is developed that links the size and distribution of the root system to the capture of water and nitrogen (which are assumed to be evenly distributed with depth) during grain filling, and allows estimates of the economic consequences of this capture to be assessed. A particular feature of the model is its use of summarizing concepts, and reliance on only the minimum number of parameters (each with a clear biological meaning). The model is then used to provide an economic sensitivity analysis of possible target characteristics for manipulating root systems. These characteristics were: root distribution with depth, proportional dry matter partitioning to roots, resource capture coefficients, shoot dry weight at anthesis, specific root weight and water use efficiency. From the current estimates of parameters it is concluded that a larger investment by the crop in fine roots at depth in the soil, and less proliferation of roots in surface layers, would improve yields by accessing extra resources. The economic return on investment in roots for water capture was twice that of the same amount invested for nitrogen capture.

Models, Theoretical↗
PubMed2003

Investigating the regulation of one-carbon metabolism in Arabidopsis thaliana.

Serine (Ser) biosynthesis in C(3) plants can occur via several pathways. One major route involves the tetrahydrofolate (THF)-dependent activities of the glycine decarboxylase complex (GDC, EC 2.1.1.10) and serine hydroxymethyltransferase (SHMT, EC 2.1.2.1) with glycine (Gly) as one-carbon (1-C) source. An alternative THF-dependent pathway involves the C1-THF synthase/SHMT activities with formate as 1-C source. Here, we have investigated aspects of the regulation of these two folate-mediated pathways in Arabidopsis thaliana (L.) Heynh. Columbia using two approaches. Firstly, transgenic plants overexpressing formate dehydrogenase (FDH, EC 1.2.1.2) were used to continue our previous studies on the function of FDH in formate metabolism. The formate pool size was approximately 73 nmol (g FW)(-1) in wild type (WT) Arabidopsis plants; three independent transgenic lines had similar-sized pools of formate. Transgenic plants produced more (13)CO(2) from supplied [(13)C]formate than did WT plants but were not significantly different from WT plants in their synthesis of Ser. We concluded that FDH has no direct role in the regulation of the above two pathways of Ser synthesis; the breakdown of formate to CO(2) by the FDH reaction is the primary and preferred fate of the organic acid in Arabidopsis. The ratio between the GDC/SHMT and C1-THF synthase/SHMT pathways of Ser synthesis from [alpha-(13)C]Gly and [(13)C]formate, respectively, in Arabidopsis shoots was 21 : 1; in roots, 9 : 1. In shoots, therefore, the pathway from formate plays only a small role in Ser synthesis; in the case of roots, results indicated that the 9 : 1 ratio was as a result of greater fluxes of (13)C through both pathways together with a relatively higher contribution from the C1-THF synthase/SHMT route than in shoots. We also examined the synthesis of Ser in a GDC-deficient mutant of Arabidopsis (glyD) where the GDC/SHMT pathway was impaired. Compared with WT, glyD plants accumulated 5-fold more Gly than WT after supplying [alpha-(13)C]Gly for 24 h; the accumulation of Ser from [alpha-(13)C]Gly was reduced by 25% in the same time period. On the other hand, the accumulation of Ser through the C1-THF synthase/SHMT pathway in glyD plants was 2.5-fold greater than that in WT plants. Our experiments confirmed that the GDC/SHMT and C1-THF synthase/SHMT pathways normally operate independently in Arabidopsis plants but that when the primary GDC/SHMT pathway is impaired the alternative C1-THF synthase/SHMT pathway can partially compensate for deficiencies in the synthesis of Ser.

Aminohydrolases↗
PubMed2003

Immunotherapy of ocular myasthenia gravis reduces conversion to generalized myasthenia gravis.

BACKGROUND: Several retrospective studies have suggested that immunotherapy, including prednisolone, azathioprine and thymectomy, reduces progression of ocular myasthenia gravis to generalized myasthenia gravis. This study examines the effect of immunotherapy on generalization rates in ocular myasthenia patients who are acetylcholine receptor (AChR) antibody-positive. METHODS: Retrospective record review of 34 patients from three university-based hospitals with neurology and neuro-ophthalmology services in Australia. In all patients, positive AChR antibodies were recorded, the initial symptoms were purely ocular, and all had at least 2 years of follow-up. The patients who developed generalized myasthenia gravis were compared with those who remained purely ocular. RESULTS: There were 21 patients who developed generalized myasthenia gravis. Of these 21, only 2 (9.5%) had received prior immunotherapy. Among the 13 patients whose symptoms remained purely ocular, 10 (76.9%) had received prior immunotherapy. CONCLUSIONS: In this study, most of the patients who progressed from ocular myasthenia to generalized myasthenia had not received prior immunotherapy. This study adds weight to the call for a prospective trial of early immunotherapy in patients with ocular myasthenia.

Adult↗
PubMed2002

Rationale for and efficacy of digital arterial reconstruction in scleroderma: report of two cases.

Two patients with scleroderma, ischemic pain, non-healing digital ulceration, and digital arterial obstruction were successfully treated with peripheral sympathectomy and digital arterial reconstruction using a reversed small-caliber vein graft. Postoperatively, digital blood flow increased and ulceration healed in both patients. Peripheral sympathectomy alone may not adequately improve digital perfusion, when the benefits of decreased vasospasm are offset by the presence of digital arterial insufficiency. When technically feasible, digital arterial reconstruction improves digital blood flow in scleroderma patients in whom digital collateral circulation appears inadequate after sympathectomy.

Adult↗
PubMedDate not supplied

Gastroschisis: etiology, diagnosis, delivery options, and care.

Gastroschisis, one of the more common congenital abdominal wall defects, results in herniation of fetal abdominal viscera into the amniotic cavity. This article discusses theories about gastroschisis etiology, in utero diagnostic tools, delivery options, and postdelivery care. Included are detailed considerations regarding immediate interventions after delivery to support the infant's thermal and fluid management needs and to protect the exposed bowel. Surgical options and postoperative care issues and complications are reviewed, as are respiratory distress and vena cava compression from increased abdominal pressure, nutritional support, and interventions related to the prevention of infection. Giving birth to an infant with gastroschisis is an upsetting experience for parents. Evidence suggests, however, that with today's advances in neonatal care and nutrition and with meticulous attention, the survival rate for infants born with gastroschisis can be excellent.

Abdominal Muscles↗