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Cochrane D, Booker H, Mundel T, Barnes M. Does Intermittent Pneumatic Leg Compression Enhance Muscle Recovery after Strenuous Eccentric Exercise? Int J Sports Med 2013; 34:969-74. [DOI: 10.1055/s-0033-1337944] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Ghim YC, Schekochihin AA, Field AR, Abel IG, Barnes M, Colyer G, Cowley SC, Parra FI, Dunai D, Zoletnik S. Experimental signatures of critically balanced turbulence in MAST. PHYSICAL REVIEW LETTERS 2013; 110:145002. [PMID: 25166998 DOI: 10.1103/physrevlett.110.145002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Indexed: 06/03/2023]
Abstract
Beam emission spectroscopy (BES) measurements of ion-scale density fluctuations in the MAST tokamak are used to show that the turbulence correlation time, the drift time associated with ion temperature or density gradients, the particle (ion) streaming time along the magnetic field, and the magnetic drift time are consistently comparable, suggesting a "critically balanced" turbulence determined by the local equilibrium. The resulting scalings of the poloidal and radial correlation lengths are derived and tested. The nonlinear time inferred from the density fluctuations is longer than the other times; its ratio to the correlation time scales as ν(*i)(-0.8 ± 0.1), where ν(*i) = ion collision rate/streaming rate. This is consistent with turbulent decorrelation being controlled by a zonal component, invisible to the BES, with an amplitude exceeding those of the drift waves by ∼ ν(*i)(-0.8).
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Lawford BR, Barnes M, Swagell CD, Connor JP, Burton SC, Heslop K, Voisey J, Morris CP, Nyst P, Noble EP, Young RM. DRD2/ANKK1 Taq1A (rs 1800497 C>T) genotypes are associated with susceptibility to second generation antipsychotic-induced akathisia. J Psychopharmacol 2013; 27:343-8. [PMID: 23118020 DOI: 10.1177/0269881112463469] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Although the advent of atypical, second-generation antipsychotics (SGAs) has resulted in reduced likelihood of akathisia, this adverse effect remains a problem. It is known that extrapyramidal adverse effects are associated with increased drug occupancy of the dopamine 2 receptors (DRD2). The A1 allele of the DRD2/ANKK1, rs1800497, is associated with decreased striatal DRD2 density. The aim of this study was to identify whether the A1(T) allele of DRD2/ANKK1 was associated with akathisia (as measured by Barnes Akathisia Rating Scale) in a clinical sample of 234 patients who were treated with antipsychotic drugs. Definite akathisia (a score ≥ 2 in the global clinical assessment of akathisia) was significantly less common in subjects who were prescribed SGAs (16.8%) than those prescribed FGAs (47.6%), p < 0.0001. Overall, 24.1% of A1+ patients (A1A2/A1A1) who were treated with SGAs had akathisia, compared to 10.8% of A1- (thus, A2A2) patients. A1+ patients who were administered SGAs also had higher global clinical assessment of akathisia scores than the A1- subjects (p = 0.01). SGAs maintained their advantage over FGAs regarding akathisia, even in A1+ patients who were treated with SGAs. These results strongly suggested that A1+ variants of the DRD2/ANKK1 Taq1A allele do confer an associated risk for akathisia in patients who were treated with SGAs, and these variants may explain inconsistencies found across prior studies, when comparing FGAs and SGAs.
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Caccamo M, Barnes M, Murali S, Benza R, Kanwar M, Raina A, Agarwal R, Thompson D, Sokos G. Evaluation of End Stage Heart Failure Patients on Inotropic Therapy in the Defibrillator Era. J Heart Lung Transplant 2013. [DOI: 10.1016/j.healun.2013.01.379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Highcock EG, Schekochihin AA, Cowley SC, Barnes M, Parra FI, Roach CM, Dorland W. Zero-turbulence manifold in a toroidal plasma. PHYSICAL REVIEW LETTERS 2012; 109:265001. [PMID: 23368571 DOI: 10.1103/physrevlett.109.265001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 11/30/2012] [Indexed: 06/01/2023]
Abstract
Sheared toroidal flows can cause bifurcations to zero-turbulent-transport states in tokamak plasmas. The maximum temperature gradients that can be reached are limited by subcritical turbulence driven by the parallel velocity gradient. Here it is shown that q/ϵ (magnetic field pitch/inverse aspect ratio) is a critical control parameter for sheared tokamak turbulence. By reducing q/ϵ, far higher temperature gradients can be achieved without triggering turbulence, in some instances comparable to those found experimentally in transport barriers. The zero-turbulence manifold is mapped out, in the zero-magnetic-shear limit, over the parameter space (γ(E), q/ϵ, R/L(T)), where γ(E) is the perpendicular flow shear and R/L(T) is the normalized inverse temperature gradient scale. The extent to which it can be constructed from linear theory is discussed.
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Barnes M, Parra FI, Dorland W. Turbulent transport and heating of trace heavy ions in hot magnetized plasmas. PHYSICAL REVIEW LETTERS 2012; 109:185003. [PMID: 23215287 DOI: 10.1103/physrevlett.109.185003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Indexed: 06/01/2023]
Abstract
Scaling laws for the transport and heating of trace heavy ions in low-frequency magnetized plasma turbulence are derived and compared with direct numerical simulations. The predicted dependences of turbulent fluxes and heating on ion charge and mass number are found to agree with numerical results for both stationary and differentially rotating plasmas. Heavy ion momentum transport is found to increase with mass, and heavy ions are found to be preferentially heated, implying a mass-dependent ion temperature for very weakly collisional plasmas and for partially ionized heavy ions in strongly rotating plasmas.
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Emmerson B, McMahon K, Stark A, Barnes M, Ward W, Kealy-Bateman W. Will we ever have enough psychiatric registrars? Australas Psychiatry 2012; 20:446-7. [PMID: 23086318 DOI: 10.1177/1039856212455254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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133
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Gardener S, Gu Y, Rainey-Smith SR, Keogh JB, Clifton PM, Mathieson SL, Taddei K, Mondal A, Ward VK, Scarmeas N, Barnes M, Ellis KA, Head R, Masters CL, Ames D, Macaulay SL, Rowe CC, Szoeke C, Martins RN. Adherence to a Mediterranean diet and Alzheimer's disease risk in an Australian population. Transl Psychiatry 2012; 2:e164. [PMID: 23032941 PMCID: PMC3565821 DOI: 10.1038/tp.2012.91] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The Mediterranean diet (MeDi), due to its correlation with a low morbidity and mortality for many chronic diseases, has been widely recognised as a healthy eating model. We aimed to investigate, in a cross-sectional study, the association between adherence to a MeDi and risk for Alzheimer's disease (AD) and mild cognitive impairment (MCI) in a large, elderly, Australian cohort. Subjects in the Australian Imaging, Biomarkers and Lifestyle Study of Ageing cohort (723 healthy controls (HC), 98 MCI and 149 AD participants) completed the Cancer Council of Victoria Food Frequency Questionnaire. Adherence to the MeDi (0- to 9-point scale with higher scores indicating higher adherence) was the main predictor of AD and MCI status in multinominal logistic regression models that were adjusted for cohort age, sex, country of birth, education, apolipoprotein E genotype, total caloric intake, current smoking status, body mass index, history of diabetes, hypertension, angina, heart attack and stroke. There was a significant difference in adherence to the MeDi between HC and AD subjects (P < 0.001), and in adherence between HC and MCI subjects (P < 0.05). MeDi is associated with change in Mini-Mental State Examination score over an 18-month time period (P < 0.05) in HCs. We conclude that in this Australian cohort, AD and MCI participants had a lower adherence to the MeDi than HC participants.
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Horton TG, Barnes M, Johnson S, Kalapos PC, Link A, Cockroft KM. Feasibility and efficacy of transcranial motor-evoked potential monitoring in neuroendovascular surgery. AJNR Am J Neuroradiol 2012; 33:1825-31. [PMID: 22517278 DOI: 10.3174/ajnr.a3017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Neurophysiological monitoring for neuroendovascular procedures typically involves EEG and SSEP monitoring via cutaneous electrodes. MEP monitoring has been used less frequently because, traditionally, this has required subdural electrode placement. With the advent of transcutaneous techniques, MEP monitoring use has increased. However, little has been published regarding the use of this technique in therapeutic neuroendovascular procedures. The purpose of this study was therefore to determine whether TcMEP monitoring is feasible and efficacious in therapeutic neuroendovascular procedures. MATERIALS AND METHODS We retrospectively reviewed our data base of therapeutic neuroendovascular procedures performed with the use of TcMEP monitoring. We specifically determined the incidence of TcMEP changes compared with changes in either SSEP or EEG. We then correlated these changes to actual adverse neurologic events. RESULTS Although TcMEP monitoring was technically successful in all of the 140 patients in which it was attempted, we observed significant changes in TcMEP signals in only 1 patient. This patient experienced changes involving all 3 monitoring modalities after intraprocedural aneurysm rupture. In contrast, changes in SSEP tracings alone were found in 9 patients. Of these, 2 patients were known to be moribund before their procedures and neither recovered. Among the remaining 7 patients, temporary SSEP changes tended to correlate with temporary neurologic deficits, while permanent changes were associated with permanent or long-lasting deficits. CONCLUSIONS These results suggest that TcMEP monitoring is feasible in therapeutic neuroendovascular procedures. However, it appears that the addition of TcMEP monitoring provides no added benefit to SSEP and EEG monitoring alone.
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Martinez-Rubi Y, Gonzalez-Dominguez JM, Ansón-Casaos A, Kingston CT, Daroszewska M, Barnes M, Hubert P, Cattin C, Martinez MT, Simard B. Tailored SWCNT functionalization optimized for compatibility with epoxy matrices. NANOTECHNOLOGY 2012; 23:285701. [PMID: 22717547 DOI: 10.1088/0957-4484/23/28/285701] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We have modified single walled carbon nanotubes (SWCNTs) with well defined matrix-based architectures to improve interface interaction in SWCNT/epoxy composites. The hardener and two pre-synthesized oligomers containing epoxy and hardener moieties were covalently attached to the SWCNT walls by in situ diazonium or carboxylic coupling reactions. In this way, SWCNTs bearing amine or epoxide-terminated fragments of different molecular weights, which resemble the chemical structure of the cured resin, were synthesized. A combination of characterization techniques such as Raman and infrared absorption (FTIR) spectroscopy, elemental analysis and coupled thermogravimetry-FTIR spectroscopy were used to identify both the functional groups and degree of functionalization of SWCNTs synthesized by the laser ablation and arc-discharge methods. Depending on the type of reaction employed for the chemical functionalization and the molecular weight of the attached fragment, it was possible to control the degree of functionalization and the electronic properties of the functionalized SWCNTs. Improved dispersion of SWCNTs in the epoxy matrix was achieved by direct integration without using solvents, as observed from optical microscopy and rheology measurements of the SWCNT/epoxy mixtures. Composite materials using these fillers are expected to exhibit improved properties while preserving the thermosetting architecture.
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Buchbinder A, Krebs M, Ott J, Bausch B, Hiesgen C, Reichert M, Hecker M, Mohr A, Seeger W, Barnes M, Mayer K. Modulation of acute lung injury (ALI) by lipid emulsions - dependency of the chemerin 23 receptor (ChemR23)? Pneumologie 2012. [DOI: 10.1055/s-0032-1315463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Fung AM, Wilson DL, Barnes M, Walker SP. Obstructive sleep apnea and pregnancy: the effect on perinatal outcomes. J Perinatol 2012; 32:399-406. [PMID: 22361975 DOI: 10.1038/jp.2012.14] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Obstructive sleep apnea (OSA) is characterized by repeated episodes of upper airway obstruction, resulting in hypoxemia, hypercapnia and sleep fragmentation. Pathophysiological sequelae include sympathetic activation, increased oxidative stress and a generalized inflammatory response, culminating in endothelial dysfunction. These are the proposed mechanisms that mediate the increased risk of hypertension and cardiovascular disease among patients with OSA outside of pregnancy. It is intriguing to consider the consequences of these events on pregnancy outcomes. There is a growing literature on the impact of maternal OSA on hypertensive disorders of pregnancy, gestational diabetes and impaired fetal growth. The data, while promising, require confirmation with larger numbers to verify the findings. OSA may be an important mediator of the poor perinatal outcomes associated with maternal obesity; moreover, one which may be amenable to treatment. This review discusses OSA and summarizes the current literature linking OSA with adverse perinatal outcomes.
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Gaydos C, Barnes M, Hsieh YH, Jett-Goheen M, Quinn N, Whittle P, Hogan T. P48 Yearly trends for the internet recruitment program, http://www.iwantthekit.org—what happened to the STI prevalence? Sex Transm Infect 2012. [DOI: 10.1136/sextrans-2012-050601c.48] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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139
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Lawford BR, Barnes M, Connor JP, Heslop K, Nyst P, Young RM. Alcohol Use Disorders Identification Test (AUDIT) scores are elevated in antipsychotic-induced hyperprolactinaemia. J Psychopharmacol 2012; 26:324-9. [PMID: 21262859 DOI: 10.1177/0269881110393051] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Hyperprolactinaemia in antipsychotic treated patients with schizophrenia is a consequence of D2 receptor (DRD2) blockade. Alcohol use disorder is commonly comorbid with schizophrenia and low availability of striatal DRD2 may predispose individuals to alcohol use. In this pilot study we investigated whether hyperprolactinaemia secondary to pharmacological DRD2 blockade was associated with alcohol use disorder in 219 (178 males and 41 females) patients with schizophrenia. Serum prolactin determinations were made in patients diagnosed with schizophrenia and maintained on antipsychotic agents. Clinical assessment included demographics, family history and administration of the AUDIT (Alcohol Use Disorders Identification Test). Higher AUDIT scores were associated with prolactin-raising antipsychotic medication (n=106) compared with prolactin-sparing medication (n=113). Risperidone (n=63) treated patients had higher AUDIT scores and prolactin levels than those on other atypical antipsychotics (n = 113). Across the entire sample, patients with a prolactin greater than 800 mIU/L had higher AUDIT scores and were more likely to exceed the cut-off score for harmful and hazardous alcohol use. These differences were not explained by potential confounds related to clinical features and demographics, comorbidity or medication side-effects. These data suggest that by lowering dosage, or switching to another antipsychotic agent, the risk for alcohol use disorder in those with schizophrenia may be reduced. This hypothesis requires testing using a prospective methodology.
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141
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Wu F, Boehling N, Nabavizadeh N, Lamborn K, Barnes M, Chang S, McDermott M, Haas-Kogan D. Clinical Outcome and Prognostic Factors for Central Neurocytoma. Int J Radiat Oncol Biol Phys 2011. [DOI: 10.1016/j.ijrobp.2011.06.1757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Porter GW, Lewis A, Barnes M, Williams R. Evaluation of high power ultrasound porous cleaning efficacy in American oak wine barrels using X-ray tomography. INNOV FOOD SCI EMERG 2011. [DOI: 10.1016/j.ifset.2011.06.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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143
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Barnes M, Parra FI, Schekochihin AA. Critically balanced ion temperature gradient turbulence in fusion plasmas. PHYSICAL REVIEW LETTERS 2011; 107:115003. [PMID: 22026680 DOI: 10.1103/physrevlett.107.115003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Indexed: 05/31/2023]
Abstract
Scaling laws for ion temperature gradient driven turbulence in magnetized toroidal plasmas are derived and compared with direct numerical simulations. Predicted dependences of turbulence fluctuation amplitudes, spatial scales, and resulting heat fluxes on temperature gradient and magnetic field line pitch are found to agree with numerical results in both the driving and inertial ranges. Evidence is provided to support the critical balance conjecture that parallel streaming and nonlinear perpendicular decorrelation times are comparable at all spatial scales, leading to a scaling relationship between parallel and perpendicular spatial scales. This indicates that even strongly magnetized plasma turbulence is intrinsically three dimensional.
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Barnes M, Ducan D, Agreda P, Hsieh YH, Holden J, Rompalo A, Gaydos C. P3-S6.04 Use of a point of care test device to detect syphilis in a STD clinic. Br J Vener Dis 2011. [DOI: 10.1136/sextrans-2011-050108.478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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145
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Hsieh YH, Barnes M, Jett-Goheen M, Quinn N, Agreda P, Whittle P, Hogan T, Gaydos C. P1-S6.18 Characteristics of men who seek rescreening for STIs after once using the http://www.iwantthekit.org screening program. Br J Vener Dis 2011. [DOI: 10.1136/sextrans-2011-050108.242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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146
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Ladd J, Hsieh YH, Barnes M, Agreda P, Quinn N, Whittle P, Jett-Goheen M, Hogan T, Gaydos C. O1-S07.02 Characteristics of women testing positive for rectal STIs using self-collected mailed specimens. Br J Vener Dis 2011. [DOI: 10.1136/sextrans-2011-050109.38] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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147
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Gaydos C, Hsieh YH, Barnes M, Jett-Goheen M, Quinn N, Agreda P, Whittle P, Hogan T. P1-S6.15 Characteristics and predictors of women seeking rescreening for stis after using the http://www.iwantthekit.org program: were they infected or uninfected? Br J Vener Dis 2011. [DOI: 10.1136/sextrans-2011-050108.239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Williamson PA, Vaidyanathan S, Clearie K, Barnes M, Lipworth BJ. Airway dysfunction in nasal polyposis: a spectrum of asthmatic disease? Clin Exp Allergy 2011; 41:1379-85. [PMID: 21676042 DOI: 10.1111/j.1365-2222.2011.03793.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Chronic rhinosinusitis with nasal polyposis (CRSwNP) represents an interesting model to investigate the existence of a non-allergic unified airway. The factors associated with airway dysfunction in CRSwNP are not fully understood. OBJECTIVE To assess the impact of nasal disease on lower airway dysfunction in CRSwNP. METHODS Fifty-seven patients with CRSwNP underwent spirometry, nasal endoscopy, exhaled nitric oxide, methacholine bronchial challenge, blood sampling for total IgE, eosinophil count and radioallergosorbent testing (NCT00788749). Three phenotypic groups were identified: 'asthma group' (asthma diagnosis); 'inflammatory group' [no asthma diagnosis, but elevated fractionated exhaled nitric oxide (FE(NO)) and/or bronchial-hyperreactivity (BHR)]; and 'non-inflammatory group' (no asthma diagnosis, no BHR and normal FE(NO)). Group comparisons, univariate and multivariate analyses were performed to examine associations with airway dysfunction. RESULTS FEV(1) and FEF(25-75%) were reduced in asthma, but there was no difference between the non-asthmatic groups. Total IgE and eosinophils were elevated in asthma vs. the non-inflammatory group, but there was no difference for asthma vs. inflammatory groups. BHR was the only significant predictor of FEV(1) (P<0.001). For FEF(25-75), BHR and eosinophil count were independent predictors (P<0.001 and P=0.04). Nasal outcomes were not predictors of spirometry. CONCLUSION AND CLINICAL RELEVANCE In CRSwNP there is asymptomatic airway dysfunction suggestive of an asthmatic phenotype. Impairment of lung function is significantly associated with BHR and eosinophilia but not parameters of nasal disease suggesting that severity of airway dysfunction relates to the spectrum of asthma rather than rhinosinusitis. Lower airway dysfunction is common in CRSwNP but does not correlate to the severity of nasal disease. Signs and symptoms of asthma should be sought and treated in CRSwNP.
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Barnes M, Parra FI, Highcock EG, Schekochihin AA, Cowley SC, Roach CM. Turbulent transport in tokamak plasmas with rotational shear. PHYSICAL REVIEW LETTERS 2011; 106:175004. [PMID: 21635042 DOI: 10.1103/physrevlett.106.175004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Indexed: 05/30/2023]
Abstract
Nonlinear gyrokinetic simulations are conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, indicating an optimal E×B shear value for plasma confinement. Local maxima in the momentum fluxes are observed, implying the possibility of bifurcations in the E×B shear. The critical temperature gradient for the onset of turbulence increases with flow shear at low flow shears; at higher flow shears, the dependence of heat flux on temperature gradient becomes less stiff. The turbulent Prandtl number is found to be largely independent of temperature and flow gradients, with a value close to unity.
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Parra FI, Barnes M, Highcock EG, Schekochihin AA, Cowley SC. Momentum injection in tokamak plasmas and transitions to reduced transport. PHYSICAL REVIEW LETTERS 2011; 106:115004. [PMID: 21469870 DOI: 10.1103/physrevlett.106.115004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Indexed: 05/30/2023]
Abstract
The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The transition happens when there is sufficient momentum input so that the velocity shear can suppress or reduce the turbulence. However, it is possible to drive too much velocity shear and rekindle the turbulent transport. The optimal level of momentum injection is determined. The reduction in transport is maximized in the regions of low or zero magnetic shear.
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