Enhanced Transmission and Reflection of Femtosecond Pulses by a Single Slit

We show that a physical mechanism responsible for the enhanced transmission and reflection of femtosecond pulses by a single subwavelength nanoslit in a thick metallic film is the Fabry-Perot-like resonant excitation of stationary, quasistationary and nonstationary waves inside the slit, which leads to the field enhancement inside and around the slit. The mechanism is universal for any pulse-scatter system, which supports the stationary resonances. We point out that there is a pulse duration limit below which the slit does not support the intraslit resonance.Comment: 4 pages, 3 figure

Resonant backward scattering of light by a two-side-open subwavelength metallic slit

The backward scattering of TM-polarized light by a two-side-open subwavelength slit in a metal film is analyzed. We show that the reflection coefficient versus wavelength possesses a Fabry-Perot-like dependence that is similar to the anomalous behavior of transmission reported in the study [Y. Takakura, Phys. Rev. Lett. \textbf{86}, 5601 (2001)]. The open slit totally reflects the light at the near-to-resonance wavelengths. In addition, we show that the interference of incident and resonantly backward-scattered light produces in the near-field diffraction zone a spatially localized wave whose intensity is 10-10$^3$ times greater than the incident wave, but one order of magnitude smaller than the intra-cavity intensity. The amplitude and phase of the resonant wave at the slit entrance and exit are different from that of a Fabry-Perot cavity.Comment: 5 figure

A Methodology to Estimate Changes in Statistical Life Expectancy Due to the Control of Particulate Matter in Air Pollution

Studies in the United States have shown that those living in less polluted cities live longer than those living in more polluted cities. After adjustments for other factors, an association remained between ambient concentrations of fine particles and shorter life expectancy. This paper presents a methodology to apply the findings of these epidemiological studies to scenarios to control fine particulate matter in Europe and to estimate the resulting losses in statistical life expectancy that can be attributed to particulate matter pollution. Calculations are carried out for all of Europe with a 50*50 km resolution, distinguishing higher PM2.5 levels in urban areas. The methodology uses population statistics and projections from the United Nations, and applies changes in mortality risk identified by the epidemiological studies to the life tables for the individual countries. The preliminary implementation suggests that, for constant 1990 pollution levels, statistical life expectancy is reduced by approximately 500 days (95 percent confidence interval ranging from 168 - 888 days). By 2010, the control measures presently decided for emissions of primary particles and the precursors of secondary aerosols are expected to reduce these losses to about 280 days (94 -497), while the theoretical maximum technically feasible emission reductions could bring reduced life expectancy below 200 (65 -344) days. While the quantifications in this study must be considered as preliminary, the methodology will allow the introduction of health impacts from fine particulate matter into a multi-pollutant/multi-effect framework so that control measures can be explored taking full account of their ancillary benefits for acidification, eutrophication and ground-level ozone

The impact of air pollutant and methane emission controls on tropospheric ozone and radiative forcing: CTM calculations for the period 1990-2030

To explore the relationship between tropospheric ozone and radiative forcing with changing emissions, we compiled two sets of global scenarios for the emissions of the ozone precursors methane (CH₄), carbon monoxide (CO), non-methane volatile organic compounds (NMVOC) and nitrogen oxides (NO_x) up to the year 2030 and implemented them in two global Chemistry Transport Models. The 'Current Legislation' (CLE) scenario reflects the current perspectives of individual countries on future economic development and takes the anticipated effects of presently decided emission control legislation in the individual countries into account. In addition, we developed a 'Maximum technically Feasible Reduction' (MFR) scenario that outlines the scope for emission reductions offered by full implementation of the presently available emission control technologies, while maintaining the projected levels of anthropogenic activities. Whereas the resulting projections of methane emissions lie within the range suggested by other greenhouse gas projections, the recent pollution control legislation of many Asian countries, requiring introduction of catalytic converters for vehicles, leads to significantly lower growth in emissions of the air pollutants NO_x, NMVOC and CO than was suggested by the widely used and more pessimistic IPCC (Intergovernmental Panel on Climate Change) SRES (Special Report on Emission Scenarios) scenarios (Nakicenovic et al., 2000), which made Business-as-Usual assumptions regarding emission control technology. With the TM3 and STOCHEM models we performed several long-term integrations (1990-2030) to assess global, hemispheric and regional changes in CH₄, CO, hydroxyl radicals, ozone and the radiative climate forcings resulting from these two emission scenarios. Both models reproduce broadly the observed trends in CO, and CH₄ concentrations from 1990 to 2002. <P style='line-height: 20px;'> For the 'current legislation' case, both models indicate an increase of the annual average ozone levels in the Northern Hemisphere by 5ppbv, and up to 15ppbv over the Indian sub-continent, comparing the 2020s (2020-2030) with the 1990s (1990-2000). The corresponding higher ozone and methane burdens in the atmosphere increase radiative forcing by approximately 0.2 Wm^-2. Full application of today's emissions control technologies, however, would bring down ozone below the levels experienced in the 1990s and would reduce the radiative forcing of ozone and methane to approximately -0.1 Wm^-2. This can be compared to the 0.14-0.47 Wm^-2 increase of methane and ozone radiative forcings associated with the SRES scenarios. While methane reductions lead to lower ozone burdens and to less radiative forcing, further reductions of the air pollutants NO_x and NMVOC result in lower ozone, but at the same time increase the lifetime of methane. Control of methane emissions appears an efficient option to reduce tropospheric ozone as well as radiative forcing

From event analysis to global lessons: disaster forensics for building resilience

With unprecedented growth in disaster risk, there is an urgent need for enhanced learning about and understanding disasters, particularly in relation to the trends in the drivers of increasing risk. Building on the disaster forensics field, we introduce the Post Event Review Capability (PERC) methodology for systematically and holistically analyzing disaster events, and identifying actionable recommendations. PERC responds to a need for learning about the successes and failures in disaster risk management and resilience, and uncovers the underlying drivers of increasing risk. We draw generalizable insights identified from seven applications of the methodology to date, where we find that across the globe policy makers and practitioners in disaster risk management face strikingly similar challenges despite variations in context, indicating encouraging potential for mutual learning. These lessons highlight the importance of integrated risk reduction strategies. We invite others to utilize the freely available PERC approach and contribute to building a repository of learnings on disaster risk management and resilience. This discussion paper is under review for the journal Natural Hazards and Earth System Sciences (NHESS)