Self-organized Criticality and Absorbing States: Lessons from the Ising Model

We investigate a suggested path to self-organized criticality. Originally, this path was devised to "generate criticality" in systems displaying an absorbing-state phase transition, but closer examination of the mechanism reveals that it can be used for any continuous phase transition. We used the Ising model as well as the Manna model to demonstrate how the finite-size scaling exponents depend on the tuning of driving and dissipation rates with system size.Our findings limit the explanatory power of the mechanism to non-universal critical behavior.Comment: 5 pages, 2 figures, REVTeX

Variations in the hospital management of self harm in adults in England: observational study

More than 140 000 people present to hospital after an episode of self harm each year in England and Wales. Improving the general hospital management of these people is a key area in preventing suicide. Although professional consensus has been reached on how self harm services should be organised and delivered, wide variations in care delivery have been reported in two regions in England. Using a nationally representative sample, we investigated the variation in services and delivery of care for self harm patients in hospitals in England

THE EFFECT OF ENVIRONMENTAL WASTE DISCHARGE ON THE HYDROCHEMISTRY OF AGBOYI CREEK, LAGOS STATE

The natural aquatic systems are extensively contaminated with heavy metals released from domestic, industrial and other man-made activities and this may have devastating effects on the ecological balance of the recipient environment and a diversity of aquatic organisms. This study therefore, investigated the presence of heavy metals in relation to environmental waste discharge in Agboyi creek and other physico-chemical parameters in order to draw a good management plan for the water body. Water samples were collected from December 2005 to June 2007, within a depth of 30cm, at 9 points using sampling bottles (2L). Some parameters such as Temperature, Transparency, Total Dissolved Solid (TDS), Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Iron (Fe), Zinc (Zn), Cadmium (Cd), and Lead (Pb) were determined in triplicates as described by APHA (1998). The result revealed that temperature was fairly constant during the dry (28oC ª¤¡Þ0.01) and wet (29oCª¤¡Þ0.02) seasons, TDS range between 94.00 mgL-1 ª¤¡Þ2.02 in dry season and 92.00ª¤¡Þ1.06 in wet season. Dissolved oxygen was 5.20ª¤¡Þ0.21 and 5.40ª¤¡Þ0.32 for dry and wet season respectively. Transparency was higher during the dry season (1.20m ª¤¡Þ 0.07) than the wet season (1.10ª¤¡Þ0.03). All water quality parameters analyzed vary insignificantly (P>0.05). The concentration of Fe (2.35ª¤¡Þ0.04 and 3.90ª¤¡Þ0.09) and Cd (0.06ª¤¡Þ0.01 and 0.09ª¤¡Þ0.02) were higher during the dry season than the wet season respectively. Zinc is negatively correlated with lead (r = -0.6532) and Cadium (r = -0.1361). The physico-chemical status of Agboyi creek can be attributed to unregulated human activities whose resultant effect on the aquatic organisms may be devastating if not controlled

Three years of greenhouse gas column-averaged dry air mole fractions retrieved from satellite – Part 2: Methane

Carbon dioxide (CO2) and methane (CH4) are the two most important anthropogenic greenhouse gases. SCIAMACHY on ENVISAT is the first satellite instrument whose measurements are sensitive to concentration changes of the two gases at all altitude levels down to the Earth's surface where the source/sink signals are largest. We have processed three years (2003–2005) of SCIAMACHY near-infrared nadir measurements to simultaneously retrieve vertical columns of CO2 (from the 1.58 µm absorption band), CH4 (1.66 µm) and oxygen (O2 A-band at 0.76 µm) using the scientific retrieval algorithm WFM-DOAS. We show that the latest version of WFM-DOAS, version 1.0, which is used for this study, has been significantly improved with respect to its accuracy compared to the previous versions while essentially maintaining its high processing speed (~1 min per orbit, corresponding to ~6000 single measurements, and per gas on a standard PC). The greenhouse gas columns are converted to dry air column-averaged mole fractions, denoted XCO2 (in ppm) and XCH4 (in ppb), by dividing the greenhouse gas columns by simultaneously retrieved dry air columns. For XCO2 dry air columns are obtained from the retrieved O2 columns. For XCH4 dry air columns are obtained from the retrieved CO2 columns because of better cancellation of light path related errors compared to using O2 columns retrieved from the spectrally distant O2 A-band. Here we focus on a discussion of the XCH4 data set. The XCO2 data set is discussed in a separate paper (Part 1). For 2003 we present detailed comparisons with the TM5 model which has been optimally matched to highly accurate but sparse methane surface observations. After accounting for a systematic low bias of ~2% agreement with TM5 is typically within 1–2%. We investigated to what extent the SCIAMACHY XCH4 is influenced by the variability of atmospheric CO2 using global CO2 fields from NOAA's CO2 assimilation system CarbonTracker. We show that the CO2 corrected and uncorrected XCH4 spatio-temporal pattern are very similar but that agreement with TM5 is better for the CarbonTracker CO2 corrected XCH4. In line with previous studies (e.g., Frankenberg et al., 2005b) we find higher methane over the tropics compared to the model. We show that tropical methane is also higher when normalizing the CH4 columns with retrieved O2 columns instead of CO2. In consistency with recent results of Frankenberg et al. (2008b) it is shown that the magnitude of the retrieved tropical methane is sensitive to the choice of the spectroscopic line parameters of water vapour. Concerning inter-annual variability we find similar methane spatio-temporal pattern for 2003 and 2004. For 2005 the retrieved methane shows significantly higher variability compared to the two previous years, most likely due to somewhat larger noise of the spectral measurement

Measurement of spray combustion processes

A free jet configuration was chosen for measuring noncombusting spray fields and hydrocarbon-air spray flames in an effort to develop computational models of the dynamic interaction between droplets and the gas phase and to verify and refine numerical models of the entire spray combustion process. The development of a spray combustion facility is described including techniques for laser measurements in spray combustion environments and methods for data acquisition, processing, displaying, and interpretation

Capacity Utilization, Industrial Production Index and Dividend Payout Policy in Nigeria: An Autoregressive Distributed Lag (ARDL) Model Approach to Cointegration

The study apply the Autoregressive Distributed Lag (ARDL) Model approach to cointegration analysis and  Error Correction Model (ECM) to examine the relationships between dividend payout policy, capacity utilization and the industrial production index for Nigeria. The cumulative sum of recursive residuals (CUSUM) and the Cumulative Sum of Squares of Recursive Residuals (CUSUMSQ) were used to test for structural stability of the model. The results from the ADF unit root tests indicate that the average dividend yield and the industrial production index are first difference stationary while capacity utilization is an I(0) variable. The ARDL bounds tests suggest that the average dividend yield, capacity utilization and the industrial production index series are cointegrated. The ECM also reveals that capacity utilization and the industrial production index have significant causative implications for dividend payout policy. The CUSUM and CUSUMSQ plots lie within the 5 per cent critical bound thus providing evidence that the parameters of the model do not suffer from any structural instability over the period of study. The analysis suggests that policies designed to increase the capacity utilization rate should be favourable for the dividend payout policy of firms in Nigeria.  These might include government policies aimed at developing infrastructure, creating enabling environment for effective and profitable productive activities to grow as well as the ability to operate at optimal capacity as a sin-qua-non to achieving policy objectives by firms. Keywords: Capacity Utilization, Industrial Production Index, Dividend Payout Polic

Promoting independent learning skills using video on digital language laboratories

This is the author's PDF version of an article published in Computer assisted language learning ©2006. The definitive version is available at http://www.informaworld.com/The article discusses the potential for developing independent learning skills using the digital language laboratory with particular reference to exploiting the increasingly available resource of digital video. It investigates the potential for recording and editing video clips from online sources and digitalising clips from analogue recordings and reflects on the current status quo regarding the complex copyright regulations in this area. It describes two pilot self-access programmes based on video clips which were undertaken with University College Chester undergraduates and reflects on the value of the experience for students in developing a wide range of language skills as well as independent learning skills using their feedback on the experience