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Trafficking of lung dendritic cells (DCs) to the draining lymph node (dLN) is a crucial step for the initiation of T cell responses upon pathogen challenge. However, little is known about the factors that regulate lung DC migration to the dLN. In this study, using a model of influenza infection, we demonstrate that complement component C3 is critically required for efficient emigration of DCs from the lung to the dLN. C3 deficiency affect lung DC-mediated viral antigen transport to the dLN, resulting in severely compromised priming of virus-specific T cell responses. Consequently, C3-deficient mice lack effector T cell response in the lungs that affected viral clearance and survival. We further show that direct signaling by C3a and C5a through C3aR and C5aR respectively expressed on lung DCs is required for their efficient trafficking. However, among lung DCs, only CD103(+) DCs make a significant contribution to lung C5a levels and exclusively produce high levels of C3 and C5 during influenza infection. Collectively, our findings show that complement has a profound impact on immune regulation by controlling tissue DC trafficking and highlights a potential utility for complement as an adjuvant in novel vaccine strategies.

Many students need assistance in debugging to achieve progress when they learn to write computer programs. Face-to-face interactions with individual students to give feedback on their programs, although definitely effective in facilitating their learning, are becoming difficult to achieve with ever-growing class sizes. This paper proposes a novel approach to providing practical automated debugging advice to support students' learning, based on the strong relationship observed between common wrong outputs and the corresponding common bugs in students' programs. To implement the approach, we designed a generic system architecture and process, and developed a tool called Virtual Debugging Advisor (ViDA) that was put into use in classes in a university. To evaluate the effectiveness of ViDA, a controlled experiment and a survey were conducted with first year engineering students in an introductory computer programming course. Results are encouraging, showing that (a) a higher proportion of students could correct their faulty code themselves with ViDA enabled, (b) an overwhelming majority of respondents found ViDA helpful for their learning of programming, and (c) most respondents would like to keep ViDA enabled when they practice writing programs.

This paper presents the first results of the measurements of trace gases and aerosols at three surface sites in and outside Beijing before and during the 2008 Olympics. The official air pollution index near the Olympic Stadium and the data from our nearby site revealed an obvious association between air quality and meteorology and different responses of secondary and primary pollutants to the control measures. Ambient concentrations of vehicle-related nitrogen oxides (NO(x)) and volatile organic compounds (VOCs) at an urban site dropped by 25% and 20-45% in the first two weeks after full control was put in place, but the levels of ozone, sulfate and nitrate in PM(2.5) increased by 16%, 64%, 37%, respectively, compared to the period prior to the full control; wind data and back trajectories indicated the contribution of regional pollution from the North China Plain. Air quality (for both primary and secondary pollutants) improved significantly during the Games, which were also associated with the changes in weather conditions (prolonged rainfall, decreased temperature, and more frequent air masses from clean regions). A comparison of the ozone data at three sites on eight ozone-pollution days, when the air masses were from the southeast-south-southwest sector, showed that regional pollution sources contributed > 34-88% to the peak ozone concentrations at the urban site in Beijing. Regional sources also contributed significantly to the CO concentrations in urban Beijing. Ozone production efficiencies at two sites were low (similar to 3 ppbv/ppbv), indicating that ozone formation was being controlled by VOCs. Compared with data collected in 2005 at a downwind site, the concentrations of ozone, sulfur dioxide (SO(2)), total sulfur (SO(2)+PM(2.5) sulfate), carbon monoxide (CO), reactive aromatics (toluene and xylenes) sharply decreased (by 8-64%) in 2008, but no significant changes were observed for the concentrations of PM(2.5), fine sulfate, total odd reactive nitrogen (NO(y)), and longer lived alkanes and benzene. We suggest that these results indicate the success of the government's efforts in reducing emissions of SO(2), CO, and VOCs in Beijing, but increased regional emissions during 2005-2008. More stringent control of regional emissions will be needed for significant reductions of ozone and fine particulate pollution in Beijing.

The professional activities that constitute the work of school teachers are known to be both numerous and varied. While managing teacher workloads is a major priority for governments around the world, valid and reliable figures are difficult to obtain. From a larger qualitative study of teachers' work culture in Singapore, we report data obtained from six teachers through work-shadowing methods. The latter we argue overcomes weaknesses in existing research using pre-determined survey categories. Our results showed that the professional work of these teachers were as varied (although variable across the year) as their counterparts elsewhere and that the total time spent on work activities ranged from 45 to 65 h per week. While this upper limit seemed slightly higher than that from other locations in the developed world such as the UK, the findings based on our sample do not support the claim that teachers in Singapore--a highly achieving system--devote considerably more time than school teachers elsewhere.

The concept of interaction that underlies Newton's Laws of Motion is compared with the students' commonsense ideas of force and motion. An approach to teaching Newton's Third Law of Motion is suggested that focuses on refining the student's intuitive thinking on the nature of interaction.