e-Pedagogy: the pedagogies of e-learning

The aim of this research was to establish effective e-learning practice in higher education. This was achieved by looking at examples of different pedagogic techniques employed in several cases. The effectiveness of these techniques was established by looking at the students' outcomes on these courses. This study has adopted a sequential mixed methodology characterized by an initial phase of qualitative data collection and analysis, which was followed by a phase of quantitative data collection and analysis. The first phase of the study involved collecting a year of data from a postgraduate programme. A grounded approach was used to analyse one million words of online conferences or discussions, and led to the emergence of 29 pedagogic behaviours. These pedagogic behaviours were then developed into a coding instrument. The second phase, hypothetico-deductive analysis, confirmed their presence in three other cases, five million words of online interactions, and established their associations with students' learning and outcomes. The findings suggest seven clusters of pedagogies correlated with students' grades and the effect size calculation revealed an educational significance for all of them. This indicates that if they are employed in online classrooms they are likely to enhance students' learning and outcomes

On Achievable Rates of the Two-user Symmetric Gaussian Interference Channel

We study the Han-Kobayashi (HK) achievable sum rate for the two-user symmetric Gaussian interference channel. We find the optimal power split ratio between the common and private messages (assuming no time-sharing), and derive a closed form expression for the corresponding sum rate. This provides a finer understanding of the achievable HK sum rate, and allows for precise comparisons between this sum rate and that of orthogonal signaling. One surprising finding is that despite the fact that the channel is symmetric, allowing for asymmetric power split ratio at both users (i.e., asymmetric rates) can improve the sum rate significantly. Considering the high SNR regime, we specify the interference channel value above which the sum rate achieved using asymmetric power splitting outperforms the symmetric case.Comment: 7 pages, to appear in Allerton 201

WHO IS BENEFITING THE MOST FROM NAFTA? AN INTERVENTION TIME SERIES ANALYSIS

Unlike previous studies on the North American Free Trade Agreement (NAFTA), which examined either trade or income effects by using forecasted trade values, this paper investigates the impact of NAFTA on both bilateral trade and income of each member country - US, Canada, and Mexico - by using historical data. This paper covers time series data before and after NAFTA was formed, from 1980 to 1999. We consider NAFTA as a prolonged impulse function in international trade activities among the three trading partners by employing an intervention-function model. Findings reveal that NAFTA increases bilateral trade between US-Canada and US-Mexico, and in terms of income, NAFTA benefits Canada the most ¡°certainly¡±. To substantiate these findings, Granger causality analysis is employed, which in turn supports our intervention-function results.NAFTA, Intervention-function Model, Time Series Analysis, Granger Causality

Adult intussusception caused by small bowel lipoma: A case study

Intussusception in the adult population is an uncommon condition that can present with nonspecific signs and symptoms, both acute and chronic. We present a case of small bowel intussusception due to an underlying submucosal lipoma in an otherwise well 64-year-old lady who presented to the emergency department with a 5-day history of central abdominal pain, nausea, and vomiting with decreasing bowel motions and flatus over the past 2 days. Computed tomography suggested a small bowel obstruction secondary to an intussusception and a small bowel resection was performed. The histopathology revealed a benign submucosal lipoma of the small bowel as a lead point for a small bowel intussusception. Small bowel intussusception is not often considered in the context of a patient presenting with abdominal pain. Its treatment in the adult population, as opposed to the pediatric population, is surgical resection as it is important to exclude an underlying malignancy

Geobacter sulfurreducens can protect 304L stainless steel against pitting in conditions of low electron acceptor concentrations

The effect of Geobacter sulfurreducens cells was studied on the electrochemical behaviour of 304L stainless steel, emphasizing the role of the soluble electron acceptor (fumarate). In fumarate-lacking media, the presence of G. sulfurreducens induced free potential ennoblement in a few hours. This ennoblement has already been observed in standard media that contained fumarate. Our previous studies have shown that G. sulfurreducens shifted the pitting potential toward the positive values. The pits induced by the presence of the bacteria were wider and deeper than in the absence of bacteria. Here, in fumarate-lacking media, similar shift in pitting potential was observed, but the repassivation phase was strongly improved. AFM analysis showed that pits were identical with those observed in the absence of bacteria at lower potential. In contrast with all the previous work where G. sulfurreducens enhanced corrosion, here at a low concentration of electron acceptor, the presence of the bacteria protected the steel against pitting

Possible role of Geobacter sulfurreducens in anaerobic corrosion of steels

Geobacteraceae are the most widespread microorganisms in soils and sediments in which microbial reduction of Fe(III) is an important process, either in the natural degradation of organic compounds or in their bioremediation. Geobacter species have been shown to be predominant microorganisms on electrodes harvesting electricity from the sediments. They have the capability to oxidize organic electron donor to carbon dioxide transferring the electron directly to electrodes [1]. On the other side, the ability of Geobacter sulfurreducens to reduce nitrate to nitrite or fumarate to succinate with a graphite electrode serving as electron donor has also been demonstrated [2]. Direct electron transfer to solid electrodes is achieved through periplasmic and outer membrane c-type cytochromes [3]. Outer membranes proteins and even some kind of conductive pili that serve as biological nanowires are also involved in the electron transfer chains, mainly to Fe(III) and Mn(IV) oxides [4]. The aim of this study was to assess the possible influence of G. sulfurreducens on the occurrence of corrosion of steels. Experiments were performed with pure cultures of G. sulfurreducens on mild steel (XC45) and three different kinds of stainless steels (ferritic steel, 304L, 316L). In each case the free potential increased by 200 to 300 mV after the injection of the bacteria. On the contrary, control experiments performed with the injection of the sterile medium or the bacteria suspension after filtration on a 0.2 µm filter did not induce any variation in the free potential. The presence of the cell was consequently directly responsible for the potential increase of the coupons. The occurrence or not of corrosion was discussed with respect to this potential increase and the nature of the medium. Besides, preliminary results allow assessing the possibility to use G. sulfurreducens to design protective biofilms

Effect of Geobacter sulfurreducens on the microbial corrosion of mild steel, ferritic and austenitic stainless steels

The influence of Geobacter sulfurreducens was tested on the anaerobic corrosion of four different steels: mild steel 1145, ferritic steel 403 and austenitic steels 304L and 316L. Within a few hours, the presence of cells induced a free potential (Eoc) ennoblement around +0.3 V on 1145 mild steel, 403 ferritic steel and 304L austenitic steels and slightly less on 316L. The kinetics of Eoc ennoblement depended on the amount of bacteria in the inoculum, but the final potential value depended essentially on the nature of the material. This effect was due to the capacity of G. sulfurreducens to create a direct cathodic reaction on steel surfaces, extracting the electrons directly from material. The presence of bacterial cells modified the corrosion features of mild steel and ferritic steel, so that corrosion attacks were gathered in determined zones of the surface. Local corrosion was significantly enhanced on ferritic steel. Potential ennoblement was not sufficient to induce corrosion on austenitic steels. In contrast G. sulfurreducens delayed the occurrence of pitting on 304L steel because of its capability to oxidize acetate at high potential values. The electrochemical behaviour of 304L steel was not affected by the concentration of soluble electron donor (acetate, 1–10 mM) or the amount of planktonic cells; it was directly linked to the biofilm coverage. After polarization pitting curves had been recorded, microscopic observations showed that pits propagated only in the surface zones where cell settlement was the densest. The study evidenced that Geobacter sulfurreducens can control the electrochemical behaviour of steels in complex ways that can lead to severe corrosion. As Geobacteraceae are ubiquitous species in sediments and soils they should now be considered as possible crucial actors in the microbial corrosion of buried equipment

Effect of hydrogenase on the corrosion of mild steel

Losses due to corrosion are evaluated at 4% of the GDP of industrialised countries and biocorrosion may be responsible for 10% of these costs [1]. Whereas the general mechanism of anaerobic corrosion, involving iron sulphur deposits, seems now well agreed, the detailed mechanism is still unclear and the implication of hydrogenase is very controversial. The influence of a [Fe] hydrogenase from C. acetobutylicum on mild steel corrosion was studied using a galvanic cell and measuring the current and the free potential. This hydrogenase seems to induce pitting corrosion. The mechanism is discussed using activated and deactivated enzyme and the possible influence of phosphate is highlighted. In the galvanic cell, the presence of hydrogenase on the surface of only one electrode induced a galvanic current up to 10µA and the potential decreased by 500mV in the presence of phosphate. MEB and EDX analysis confirmed the presence of a vivianite deposit which forms a protective barrier to corrosion [2]. It seems that either type of hydrogenase ([Fe] or [Ni-Fe]) has a significant role in initiating corrosion [3, 4]