The IceCube Data Acquisition System: Signal Capture, Digitization, and Timestamping

IceCube is a km-scale neutrino observatory under construction at the South Pole with sensors both in the deep ice (InIce) and on the surface (IceTop). The sensors, called Digital Optical Modules (DOMs), detect, digitize and timestamp the signals from optical Cherenkov-radiation photons. The DOM Main Board (MB) data acquisition subsystem is connected to the central DAQ in the IceCube Laboratory (ICL) by a single twisted copper wire-pair and transmits packetized data on demand. Time calibration is maintained throughout the array by regular transmission to the DOMs of precisely timed analog signals, synchronized to a central GPS-disciplined clock. The design goals and consequent features, functional capabilities, and initial performance of the DOM MB, and the operation of a combined array of DOMs as a system, are described here. Experience with the first InIce strings and the IceTop stations indicates that the system design and performance goals have been achieved.Comment: 42 pages, 20 figures, submitted to Nuclear Instruments and Methods

Electrocoagulation as a green technology for phosphate removal from River water

The current study investigates the removal of phosphate from water using a new baffle plates aluminium-based electrochemical cell (PBPR) taking consideration the influence of key operating parameters. This new cell utilises perforated baffle plates as a water mixer rather than magnetic stirrers that require extra power to work. As this unit is new, a comprehensive study has been carried to assess it performance. This study also includes preliminary estimates of the reactor’s operating costs, the amount of H2 gas produced and the yieldable energy from it. SEM (scanning electron microscope) was used to investigate the influence of the electrocoagulation process on the morphology of the surface of aluminium electrodes, and an empirical model developed to reproduce the phosphate removal process. The results showed that 99% of phosphate was removed within 60 minutes of electrolysis at an initial pH (ipH) of 6, inter-electrode distance (ID) of 0.5 cm, current density (J) of 6 mA/cm2, initial concentration of phosphate (IC) of 100 mg/L, and minimum operating cost of 0.503 US $/m3. The electrochemical cell produced enough H2 gas to generate 4.34 kWh/m3 of power. Statistically, it was proved that the influence of the operating parameters on phosphate removal could be modelled with an R2 of 0.882, the influence of these operating parameters on phosphate removal following the order: t>J>IC>ipH >ID. Finally, SEM images showed that after several electrolysing runs, the Al anode became rough and nonuniform which could be related to the production of aluminium hydroxides

Measurement of atmospheric neutrino oscillations with IceCube

We present the first statistically significant detection of neutrino oscillations in the high-energy regime (>20 GeV) from an analysis of IceCube Neutrino Observatory data collected in 2010 and 2011. This measurement is made possible by the low-energy threshold of the DeepCore detector (~20 GeV) and benefits from the use of the IceCube detector as a veto against cosmic-ray-induced muon background. The oscillation signal was detected within a low-energy muon neutrino sample (20-100 GeV) extracted from data collected by DeepCore. A high-energy muon neutrino sample (100 GeV-10 TeV) was extracted from IceCube data to constrain systematic uncertainties. The disappearance of low-energy upward-going muon neutrinos was observed, and the nonoscillation hypothesis is rejected with more than 5σ significance. In a two-neutrino flavor formalism, our data are best described by the atmospheric neutrino oscillation parameters |Δm(32)(2)|=(2.3(-0.5)(+0.6))×10(-3) eV(2) and sin(2)(2θ(23))>0.93, and maximum mixing is favored.M. G. Aartsen ... G. C. Hill ... et al. (IceCube Collaboration

Measurement of the cosmic ray energy spectrum with IceTop-73

We report on the measurement of the all-particle cosmic ray energy spectrum with the IceTop air shower array in the energy range from 1.58 PeV to 1.26 EeV. The IceTop air shower array is the surface component of the IceCube Neutrino Observatory at the geographical South Pole. The analysis was performed using only information from IceTop. The data used in this work were taken from June 1, 2010 to May 13, 2011. During that period the IceTop array consisted of 73 stations, compared to 81 in its final configuration. The measured spectrum exhibits a clear deviation from a single power law above the knee around 4 PeV and below 1 EeV. We observe spectral hardening around 18 PeV and steepening around 130 PeV.M. G. Aartsen ... G. C. Hill ... et al. (IceCube Collaboration

Essays on institutional evolution and economic development: evidence from Nigeria

Includes bibliographical referencesThe important role of institutions is relatively agreed on within the growth literature, with most empirical evidence pointing towards a positive influence of institutions on economic growth. However, empirical analysis of the institutions and growth nexus have faced a few problems, which include: the lack of a clear distinction between the different types of institutions; (i.e. political institutions, economic institutions, and customary institutions); a lack of long-run data measuring institutions for most of sub-Saharan Africa; and the paucity of country specific studies - the majority of the empirical evidence have mainly focused on cross-country analysis. While extensions from cross-country analysis to country specific analysis is growing, empirical studies focused on sub-Saharan Africa remain limited. Within the African context, majority of empirical evidence suggest weak institutions as one of the main causes of its poor economic performance. However, due to the paucity of long-run data on institutions, such an hypothesis has not been empirically tested for specific countries. Motivated by these gaps, this thesis contains three essays that examine three types of institutions and their impact on the economy. The specific issues focused on include: the evolution of institutions; persistence of institutions; interdependence between political and economic institutions; interdependence between institutions and economic development; and the role of institutions in determining resource wealth effects. This thesis uses Nigeria as a case study, because of its standing as one of the larger economies in sub-Saharan Africa, especially in terms of its natural resources. In addition to this, Nigeria has experienced numerous regime and constitutional changes over the past few decades which may lead to interesting institutional dynamics

Natural gas consumption and economic growth : evidence from selected natural gas vehicle markets in Europe

In this study, the relationship between natural gas consumption (NGC) and economic growth is examined. Twelve (12) countries in Europe are considered, 10 of which make up the top natural gas vehicle (NGV) markets in Europe. The study considers four main variables in this exercise, namely; gross fixed capital formation, labour force, trade openness, and real GDP. It makes use of panel cointegration analysis and long-run vector error correction model analysis in assessing both the short-run and the long-run relationship dynamics between NGC and economic growth. The results show that a long-run impact of NGC on economic growth does indeed exist. In the short run, however, this does not seem to be the case. The results also suggest the existence of the growth hypothesis in Austria, Bulgaria and Switzerland, while the United Kingdom (UK) and Italy support the conservation hypothesis

Macroeconomic Policy effects on development transition – Views from Agent based model

Assessing the impact of a policy before implementation has often been a difficult feat to achieve, both at the macroeconomic and microeconomic levels. This challenge becomes even more daunting in the context of a developing country and has encouraged enormous amount of research over an extended period of time using different models. Traditional models for assessing the impact of policy implementation are fragmented given the assumption that factors affecting such policies are homogeneous whilst neglecting the interactions between various markets. Agent-based modelling can overcome this limitation given its capability to provide a micro-founded macroeconomic analysis of policy, within a variety of economic conditions and policy objectives to facilitate the understanding of the observed response. Against this backdrop, the current work adopts an agent based framework to investigate three distinct policies that have been employed by some advanced countries towards achieving sustainable development goals. This is carried out to derive lessons and explore opportunities for enhancing policy implementation in developing countries. Agent representation involve decisions by involve manufacturers, households (final goods consumers), banks (loan issues & bankruptcy warning), central bank (Basel monitor & monetary policy activity), government (fiscal policy role) and singular energy market supplier, which enables consideration of: the impact of unemployment benefits on the labour market; the impact of capital investment subsidy on investment levels; and the impact of energy taxes (in the form of an increase in the energy cost structure) on a developing country’s macroeconomic system. Results shows that an increase in unemployment benefits led to improvements in the labour market and reduction in wage margin, with a limitation threshold of 50%. Additionally, it was observed that the economy becomes more sensitive to energy tax due to higher unemployment benefits, although the diminishing nature of the relationship was quite noticeable

Institutions and intra-sub-regional trade: the ECOWAS Case

Extensive evidence has been found in literature for the role of institutions in determining the outcomes of a number of macroeconomic variables. This evidence is however inconclusive in the case of trade. In this paper, the gravity model of trade is employed in an empirical assessment of the relationship between institutions and intra-sub-regional trade. In this regard, the overall impact of the quality of institutions is examined, as well as the impact of the difference in quality of institutions between trading countries, on bilateral trade within the ECOWAS (Economic Community of West African States) region. The empirical results show evidence of significant impact of differences in the quality of institutions on intra-sub-regional trade

Institutions and intra-sub-regional trade: the ECOWAS Case

Extensive evidence has been found in literature for the role of institutions in determining the outcomes of a number of macroeconomic variables. This evidence is however inconclusive in the case of trade. In this paper, the gravity model of trade is employed in an empirical assessment of the relationship between institutions and intra-sub-regional trade. In this regard, the overall impact of the quality of institutions is examined, as well as the impact of the difference in quality of institutions between trading countries, on bilateral trade within the ECOWAS (Economic Community of West African States) region. The empirical results show evidence of significant impact of differences in the quality of institutions on intra-sub-regional trade

Economic geography determinants of spatial wage disparities in South Africa: Evidence from a firm-level panel

In this paper, we use the new economic geography (NEG) framework to estimate the extent to which spatial wage disparities in the South African manufacturing sector are an outcome of economic forces such as market access. To test the relationship, we use the anonymized tax data on employers and employees made available by the South African Revenue Service and National Treasury in collaboration with UNU-WIDER. We first document the key stylized facts that characterize the spatial distribution of wages across regions in South Africa using exploratory spatial data analysis (ESDA) techniques. We then test for the existence of a wage structure across South African local and metropolitan municipalities, controlling for individual and firm characteristics using a two-stage estimation method. Consistent with the NEG predictions, we find that wages are higher in municipalities that are closer to large markets, as measured by the Harris market potential index. However, much of the wage effect is driven by the income and employment density of the municipality's own market, and not that of surrounding areas. These results point to a combination of large spatial rigidities leading to highly localized effects of market potential, together with wage and productivity effects arising from urban agglomeration economies