Naresuan University Journal
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LOFAR discovery of a quiet emission mode in PSR B0823+26
No full textPSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over time-scales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing. Studying pulsars like PSR B0823+26 provides further insight into the relationship between these various emission phenomena and what they might teach us about pulsar magnetospheres. Here we report on the LOFAR (Low-Frequency Array) discovery that PSR B0823+26 has a weak and sporadically emitting `quiet' (Q) emission mode that is over 100 times weaker (on average) and has a nulling fraction forty-times greater than that of the more regularly-emitting `bright' (B) mode. Previously, the pulsar has been undetected in the Q mode, and was assumed to be nulling continuously. PSR B0823+26 shows a further decrease in average flux just before the transition into the B mode, and perhaps truly turns off completely at these times. Furthermore, simultaneous observations taken with the LOFAR, Westerbork, Lovell, and Effelsberg telescopes between 110 MHz and 2.7 GHz demonstrate that the transition between the Q mode and B mode occurs within one single rotation of the neutron star, and that it is concurrent across the range of frequencies observed
The promise of corporate entrepreneurship A review of data analytic strategies
No full textA burgeoning literature on corporate entrepreneurship has emerged since the early 1990s drawing on theoretical and empirical streams in strategic management and attributes of entrepreneurship such as decision-making under Knightian uncertainty, individual level theories of creativity and exploration, and Schumpeterian notions of creative destruction. The field has enticed increasing numbers of researchers to examine promised notions of competitive advantage, wealth creation, growth, innovation, and firm performance. This paper reviews the statistical micro-foundations of the domain to ascertain whether or not the conceptual and empirical interest in corporate entrepreneurship is outpacing the quality of data analytic methodologies and statistical checks for robustness and validity. The review focuses on the era of blossoming in literature growth between 2000 and 2009 and concludes that while there is always room for improvement, that the statistical and analytical health of the research being performed is headed in a promising direction. This bodes well for the future of both inquiry and practice in this domain and the realization of its espoused benefits
Corticosteroid insensitive alveolar macrophages from asthma patients; synergistic interaction with a p38 mitogen-activated protein kinase (MAPK) inhibitor.
No full textAIMS: Some asthma patients remain symptomatic despite using high doses of inhaled corticosteroids (ICS). We used alveolar macrophages to identify individual patients with insensitivity to corticosteroids and to evaluate the anti-inflammatory effects of a p38 mitogen-activated protein kinase (MAPK) inhibitor combined with a corticosteroid on these cells. METHODS: Alveolar macrophages from 27 asthma patients (classified according to the Global Initiative for Asthma (GINA) treatment stage. Six GINA1, 10 GINA2 and 11 GINA3/4) were stimulated with lipoploysaccharide (LPS) (1 μg ml(-1)). The effects of dexamethasone (dex 1-1000 nm), the p38 MAPK inhibitor 1-(5-tert-butyl-2-p-tolyl-2Hpyrazol-3-yl)-3(4-(2-morpholin-4-yl-ethoxy)naphthalen-1-yl)urea (BIRB-796 1-1000 nm) and both drugs combined at all concentrations on supernatant TNFα, IL-6 and CXCL-8 concentrations were analyzed by ELISA. Dose-sparing and efficacy enhancing effects of combination treatment were determined. RESULTS: Dexamethasone reduced LPS-induced TNFα, IL-6 and CXCL-8 in all groups, but maximum inhibition was significantly reduced for GINA3/4 compared with GINA2 and GINA1 (P <0.01). A subgroup of corticosteroid insensitive patients with a reduced effect of dexamethasone on cytokine secretion were identified. BIRB-796 in combination with dexamethasone significantly increased cytokine inhibition compared with either drug alone (P <0.001) in all groups. This effect was greater in corticosteroid insensitive compared with sensitive patients. There were significant synergistic dose-sparing effects (P <0.05) for the combination treatment on inhibition of TNFα, IL-6 and CXCL-8 in all groups. There was also significant efficacy enhancing benefits (P <0.05) on TNFα and IL-6. CONCLUSIONS: p38 MAPK inhibitors synergistically enhance efficacy of corticosteroids in macrophages from asthma patients. This effect is greater in corticosteroid insensitive asthma patients, suggesting that this class of drug should be targeted to this patient phenotype
Estimation of Daytime NO3 Radical Levels in the UK Urban Atmosphere Using the Steady State Approximation Method
No full textThe steady state approximation has been applied to the UK National Environment Technology Centre (NETCEN) data at three urban sites in the UK (Marylebone Road London, London Eltham, and Harwell) over the period of 1997 to 2012 to estimate the concentrations of daytime NO3. Despite the common assertion that NO3 levels are negligible in the day as a consequence of photolysis, there are occasions where NO3 reaches a few pptv. A seasonal pattern in NO3 concentration was observed with higher levels in the spring with consistent peaks in April and May. A combination of temperature effects (the formation of NO3 from the reaction of NO2 with O-3 has a high activation energy barrier), a distinct pattern in O-3 concentration (peaking in spring), and loss via reaction with NO peaking in winter is responsible for this trend. Although reaction with OH is still the dominant loss process for VOCs during the day, there are VOCs (unsaturated) that will have an appreciable loss due to reaction with NO3 in the daytime. Since the addition reaction of NO3 with alkenes can lead directly to organic nitrate formation, there are implications for O-3 formation and secondary organic aerosol formation during daytime and these are discussed
Purinergic neurone-glia signalling in cognitive-related pathologies
No full textNeuroglia, represented by astrocytes, oligodendrocytes, NG glia and microglia are homeostatic, myelinating and defensive cells of the brain. neuroglial cells express various combinations of purinoceptors, which contribute to multiple intercellular signalling pathways in the healthy and diseased nervous system. Neurological diseases are invariably associated with profound neuroglial remodelling, which is manifest by reactive gliosis, pathological remodelling and functional atrophy of various types of glial cells. Gliopathology is disease and region specific and produces multiple glial phenotypes that may be neuroprotective or neurotoxic. In this review we summarise recent knowledge on the role of glial purinergic signalling in cognitive related neurological diseases