Urban snowmelt processes – current research and modelling needs

Despite the water balances of cold region towns being dominated by low intensity, long duration snowmelt events, urban drainage systems continue to be designed according to standards developed for short, high intensity rain storms. During the 1980s and early 1990s, work in Scandinavia (Bengtsson, 1983, 1984, 1986; Westerström, 1984; Bengtsson and Westerström, 1992; Thorolfsson, 1990) and Canada (Xu and Buttle, 1987; Buttle and Xu, 1988, Todhunter et al., 1992) identified fundamental differences between rural and urban snowmelt processes. They found that snow properties such as density and albedo varied both between town and country and within the town depending on land-use. Moreover, both the longwave and shortwave radiation balances are heavily modified by buildings. Thus melt and runoff generation occurs at different times and rates. Town centres can have melt rates almost double that of residential areas. Despite snow removal policies, snowmelt in town centres is extremely important as these areas are the most likely to have combined sewer systems. These revelations will come as no surprise to practitioners working in cold regions, however, there is a lack of published material. This paper documents urban snow research from the last decade, it is both a summary and continuation of the state-of-the-art review found in a UNESCO special report on urban drainage in cold regions (Chapter 2, Semadeni-Davies and Bengtsson, 2000). Topics discussed include snow distribution, snow energy balance, frozen soil and runoff generation and modelling approaches - water quality issues are outside the scope. How to improve temporal and spatial resolution with limited budgets and limited data availability are ongoing problems, however, recent coupling between major urban drainage models such as SWMM and MOUSE and Geographic Information Systems offers a glimmer of hope. While full physically-based snow melt modelling is still out of the question, GIS could allow improved representations of snow distribution and energetics

Linear optical properties of Ge nanocrystals in silica

The absorption and extinctionspectra of Genanocrystals in silica formed by ion implantation are studied using photothermal deflection and transmission spectroscopies. It is found that scattering makes a significant contribution to the extinction spectrum, damping the spectral features and resulting in a Rayleigh scattering-likeω⁴ dependence. In contrast, the spectra measured by photothermal deflection clearly show features such as the E1/E1+Δ1 transitions. The Tauc gap is extracted to be ∼0.7±0.1 eV

T-type Ca 2+ channels are required for enhanced sympathetic axon growth by TNFα reverse signalling

Tumour necrosis factor receptor 1 (TNFR1)-activated TNFα reverse signalling, in which membrane-integrated TNFα functions as a receptor for TNFR1, enhances axon growth from developing sympathetic neurons and plays a crucial role in establishing sympathetic innervation. Here, we have investigated the link between TNFα reverse signalling and axon growth in cultured sympathetic neurons. TNFR1-activated TNFα reverse signalling promotes Ca2+ influx, and highly selective T-type Ca2+ channel inhibitors, but not pharmacological inhibitors of L-type, N-type and P/Q-type Ca2+ channels, prevented enhanced axon growth. T-type Ca2+ channel-specific inhibitors eliminated Ca2+ spikes promoted by TNFα reverse signalling in axons and prevented enhanced axon growth when applied locally to axons, but not when applied to cell somata. Blocking action potential generation did not affect the effect of TNFα reverse signalling on axon growth, suggesting that propagated action potentials are not required for enhanced axon growth. TNFα reverse signalling enhanced protein kinase C (PKC) activation, and pharmacological inhibition of PKC prevented the axon growth response. These results suggest that TNFα reverse signalling promotes opening of T-type Ca2+ channels along sympathetic axons, which is required for enhanced axon growth

Gravimetric phenotyping of whole plant transpiration responses to atmospheric vapour pressure deficit identifies genotypic variation in water use efficiency

There is increasing interest in rapidly identifying genotypes with improved water use efficiency, exemplified by the development of whole plant phenotyping platforms that automatically measure plant growth and water use. Transpirational responses to atmospheric vapour pressure deficit (VPD) and whole plant water use efficiency (WUE, defined as the accumulation of above ground biomass per unit of water used) were measured in 100 maize (Zea mays L.) genotypes. Using a glasshouse based phenotyping platform with naturally varying VPD (1.5 to 3.8 kPa), a 2-fold variation in WUE was identified in well-watered plants. Regression analysis of transpiration versus VPD under these conditions, and subsequent whole plant gas exchange at imposed VPDs (0.8 to 3.4 kPa) showed identical responses in specific genotypes. Genotype response of transpiration versus VPD fell into two categories: 1) a linear increase in transpiration rate with VPD with low (high WUE) or high (low WUE) transpiration rate at all VPDs, 2) a non-linear response with a pronounced change point at low VPD (high WUE) or high VPD (low WUE). In the latter group, high WUE genotypes required a significantly lower VPD before transpiration was restricted, and had a significantly lower rate of transpiration in response to VPD after this point, when compared to low WUE genotypes. Change point values were significantly positively correlated with stomatal sensitivity to VPD. A change point in stomatal response to VPD may explain why some genotypes show contradictory WUE rankings according to whether they are measured under glasshouse or field conditions. Furthermore, this novel use of a high throughput phenotyping platform successfully reproduced the gas exchange responses of individuals measured in whole plant chambers, accelerating the identification of plants with high WUE

The Real Effects of Tax Havens

It is common to summarize the impact of tax havens as a shift of tax revenues from high to low-tax jurisdictions. This chapter discusses the economic impact of tax havens that goes beyond a zero-sum transfer of the tax base, what we label real effects. We review the literature and focus on exploring how profit shifting affects employment, investment, and innovation in firms. We consider in turn how real effects shape market structure and their implications in general equilibrium. In conclusion, we propose some potential pathways for future research in terms of methodology and areas that we deem promising for further exploration

Time to First-Line ART Failure and Time to Second-Line ART Switch in the IeDEA Pediatric Cohort

BACKGROUND: Globally, 49% of the estimated 1.8 million children living with HIV are accessing antiretroviral therapy (ART). There are limited data concerning long-term durability of first-line ART regimens and time to transition to second-line. METHODS: Children initiating their first ART regimen between 2 and 14 years of age and enrolled in one of 208 sites in 30 Asia-Pacific and African countries participating in the Pediatric International Epidemiology Databases to Evaluate AIDS consortium were included in this analysis. Outcomes of interest were: first-line ART failure (clinical, immunologic, or virologic), change to second-line, and attrition (death or loss to program ). Cumulative incidence was computed for first-line failure and second-line initiation, with attrition as a competing event. RESULTS: In 27,031 children, median age at ART initiation was 6.7 years. Median baseline CD4% for children ≤5 years of age was 13.2% and CD4 count for those >5 years was 258 cells per microliter. Almost all (94.4%) initiated a nonnucleoside reverse transcriptase inhibitor; 5.3% a protease inhibitor, and 0.3% a triple nucleoside reverse transcriptase inhibitor-based regimen. At 1 year, 7.7% had failed and 14.4% had experienced attrition; by 5 years, the cumulative incidence was 25.9% and 29.4%, respectively. At 1 year after ART failure, 13.7% had transitioned to second-line and 11.2% had experienced attrition; by 5 years, the cumulative incidence was 31.6% and 25.9%, respectively. CONCLUSIONS: High rates of first-line failure and attrition were identified in children within 5 years after ART initiation. Of children meeting failure criteria, only one-third were transitioned to second-line ART within 5 years

Teaching African American Studies in the US and the UK

This is the first in what the Associate Editors hope will become a series of transatlantic exchanges about American Studies pedagogy. Conducted in the four months between January and April 2017, the discussion encompasses the political significance of African American Studies, the role of identity in the shaping of curricula and student responses to those curricula, and the challenges encountered by teachers at a variety of career stages and in a range of educational and geographic locations