Limited sensitivity of permafrost soils to heavy rainfall across Svalbard ecosystems.

Together with warming air temperatures, Arctic ecosystems are expected to experience increases in heavy rainfall events. Recent studies report accelerated degradation of permafrost under heavy rainfall, which could put significant amounts of soil carbon and infrastructure at risk. However, controlled experimental evidence of rainfall effects on permafrost thaw is scarce. We experimentally tested the impact and legacy effect of heavy rainfall events in early and late summer for five sites varying in topography and soil type on the High Arctic archipelago of Svalbard. We found that effects of heavy rainfall on soil thermal regimes are small and limited to one season. Thaw rates increased under heavy rainfall in a loess terrace site, but not in polygonal tundra soils with higher organic matter content and water tables. End-of-season active layer thickness was not affected. Rainfall application did not affect soil temperature trends, which appeared driven by timing of snowmelt and organic layer thickness, particularly during early summer. Late summer rainfall was associated with slower freeze-up and colder soil temperatures the following winter. This implies that rainfall impacts on Svalbard permafrost are limited, locally variable and of short duration. Our findings diverge from earlier reports of sustained increases in permafrost thaw following extreme rainfall, but are consistent with observations that maritime permafrost regions such as Svalbard show lower rainfall sensitivity than continental regions. Based on our experiment, no substantial in-situ effects of heavy rainfall are anticipated for thawing of permafrost on Svalbard under future warming. However, further work is needed to quantify permafrost response to local redistribution of active layer flow under natural rainfall extremes. In addition, replication of experiments across variable Arctic regions as well as long-term monitoring of active layers, soil moisture and local climate will be essential to develop a panarctic perspective on rainfall sensitivity of permafrost.

Radiation control by defects in dark-state resonant photonic lattices.

In this Letter, we present and explain novel radiation properties enabled by defects in resonant photonic lattices (PLs). Incorporating a defect breaks the lattice symmetry and generates radiation through the stimulation of leaky waveguide modes near the non-radiant bound (or dark) state spectral location. Analyzing a simple one-dimensional (1D) subwavelength membrane structure, we show that the defects produce local resonant modes that correspond to asymmetric guided-mode resonances (aGMRs) in spectra and near-field profiles. Without a defect, a symmetric lattice in the dark state is neutral, generating only background scattering. Incorporating a defect into the PL induces high reflection or transmission by robust local resonance radiation depending on the background radiation state at the bound state in the continuum (BIC) wavelengths. With the example of a lattice under normal incidence, we demonstrate defect-induced high reflection as well as high transmission. The methods and results reported here have significant potential to enable new modalities of radiation control in metamaterials and metasurfaces based on defects.

Quantifying bound and leaky states of resonant optical lattices by Rytov-equivalent homogeneous waveguides.

The properties of periodic optical lattices are generally investigated with rigorous numerical methods. For physical insight and understanding of the complex processes underlying observed spectra, simple analytical models are needed. Accordingly, we show that by applying full Rytov effective-medium formalisms, the bound and leaky states of resonant photonic lattices can be quantified with high precision. Thus, all key properties are embodied in Rytov-equivalent homogeneous waveguides. The symmetric effective-medium theory (EMT) model quantifies rigorously computed guided-mode resonance (GMR) reflectance loci defining the leaky states. The asymmetric EMT formula similarly quantifies the bound state in the continuum (BIC) loci. Even with the period and wavelength on similar scales, the analytical EMT refractive index solutions agree exactly with rigorous solutions. We apply the Rytov formulas to explain the resonant leaky band structure including appearance of GMR and BIC states as well as band transitions and band closure points. The wavenumbers of the equivalent waveguides represent the BIC embedded eigenvalues as quantified here.

Substrate-wave-induced antireflection in metasurfaces.

We address the antireflection (AR) properties of periodic surfaces, or metasurfaces, supporting substrate waves. The work is motivated by recent literature where AR bands formed by substrate-wave propagation are incorrectly attributed to Mie scattering. In contrast, as clearly shown here, substrate-wave generation with corresponding AR signatures is a diffractive effect due to a periodic lattice and is not due to particle scattering as in Mie resonance. Treating both 1D and 2D surfaces, we demonstrate a clear quantitative connection between major AR loci and corresponding total substrate transmittance loci via maps in period versus wavelength. As shown, this holds for fully dispersed, lossy surfaces as well. The results presented here serve to elucidate the physical properties of periodic metasurfaces placed on substrates admitting propagating diffraction orders and may inform the design and implementation of grating-based AR structures.

Micro-electromechanical-system-tuned resonant filters spanning the 8-12 µm band.

The spectral band covering ∼8-12µm is atmospherically transparent and therefore important for terrestrial imaging, day/night situational awareness systems, and spectroscopic applications. There is a dearth of tunable filters spanning the band. Here, we propose and demonstrate a new, to the best of our knowledge, tunable-filter method engaging the fundamental physics of the guided-mode resonance (GMR) effect realized with a non-periodic lattice. The polarization-dependent filter is fashioned with a one-dimensional Ge grating on a ZnSe substrate and interrogated with a ∼1.5mm Gaussian beam to show clear transmittance nulls. To expand the tuning range, the device parameters are optimized for sequential operation in TM and TE polarization states. The theoretical model exhibits a tunable range exceeding 4 µm, thus covering the band fully. In the experiment, a prototype device exhibits a spectral range of 8.6-10.0 µm in TM and 9.9-11.7 µm in TE polarization or >3µm total. With additional efforts in fabrication, we expect to achieve the full range.

Resonant filters with concurrently tuned central wavelengths and sidebands.

Tunable infrared filters are important for various optical and optoelectronic systems. Ideally, such filters should span wide spectral ranges while retaining constant performance. Here, as a fundamental approach, we theoretically treat tunable resonant filters and realize favorable spectral profiles. Implementing a chirped zero-contrast grating on wedged sublayers, we optimize the resonant tunable filter for operation in the ∼5-14µm band. To clarify the root causes of the physical processes enabling the observed performance, attendant resonance modal processes and background reflection behavior are analyzed in detail by equivalent models as well as by rigorous electromagnetic models. The key innovative contribution of this research is that it enables efficient filters with simultaneously tuned operational wavelengths and sidebands.

Unpolarized resonant notch filters for the 8-12 µm spectral region.

The long-wave infrared (LWIR) spectral region spanning ∼8-12µm is useful for many scientific and industrial applications. As traditional multilayer film components are not straightforwardly realized at these bands, we provide design, fabrication, and testing of polarization independent bandstop filters based on the guided-mode resonance (GMR) effect. Focusing on the zero-contrast grating architecture, we successfully fabricate prototype filters in the Ge-on-ZnSe materials system. Applying mask-based photolithography and dry etching, photoresist patterns form the desired Ge grating structures. The resulting devices exhibit clean transmittance nulls and acceptably high sidebands. Moreover, we verify polarization independent notch filtering by assembling two identical GMR filters with gratings oriented orthogonally. This approach to realize effective GMR elements will be useful for various fields including photonic and optoelectronic devices operating in the LWIR region.

Fabrication methods for infrared resonant devices.

Photonic metastructures operating in the 8-13 µm mid-infrared are fast becoming a topic of active research. However, literature describing techniques for their fabrication, which lie on a scale between nanofabrication and microelectromechanical systems technology, is scant. Here, we present detailed fabrication blueprints for achieving robust and repeatable results for devices in this region. Applying a Ge device layer on a ZnS substrate, we fabricate a materially robust transverse-magnetic-polarized wideband reflector with high reflectance in a 2.4 µm band. We then regrow a conformal layer on the device, boosting its performance to yield a ∼3 µm 90% reflectance band from 8.1 µm to 11.1 µm and a band of 98% reflectance spanning 8.7-10.4 µm. The generalized methods presented are applicable in most labs with ordinary fabrication resources.

Structural circular birefringence and dichroism quantified by differential decomposition of spectroscopic transmission Mueller matrices from Cetonia aurata.

Transmission Mueller-matrix spectroscopic ellipsometry is applied to the cuticle of the beetle Cetonia aurata in the spectral range 300-1000 nm. The cuticle is optically reciprocal and exhibits circular Bragg filter features for green light. By using differential decomposition of the Mueller matrix, the circular and linear birefringence as well as dichroism of the beetle cuticle are quantified. A maximum value of structural optical activity of 560°/mm is found.

Development of a dynamic headspace gas chromatography-mass spectrometry method for on-site analysis of sulfur mustard degradation products in sediments.

Sampling teams performing work at sea in areas where chemical munitions may have been dumped require rapid and reliable analytical methods for verifying sulfur mustard leakage from suspected objects. Here we present such an on-site analysis method based on dynamic headspace GC-MS for analysis of five cyclic sulfur mustard degradation products that have previously been detected in sediments from chemical weapon dumping sites: 1,4-oxathiane, 1,3-dithiolane, 1,4-dithiane, 1,4,5-oxadithiephane, and 1,2,5-trithiephane. An experimental design involving authentic Baltic Sea sediments spiked with the target analytes was used to develop an optimized protocol for sample preparation, headspace extraction and analysis that afforded recoveries of up to 60-90%. The optimized method needs no organic solvents, uses only two grams of sediment on a dry weight basis and involves a unique sample presentation whereby sediment is spread uniformly as a thin layer inside the walls of a glass headspace vial. The method showed good linearity for analyte concentrations of 5-200 ng/g dw, good repeatability, and acceptable carry-over. The method's limits of detection for spiked sediment samples ranged from 2.5 to 11 µg/kg dw, with matrix interference being the main limiting factor. The instrumental detection limits were one to two orders of magnitude lower. Full-scan GC-MS analysis enabled the use of automated mass spectral deconvolution for rapid identification of target analytes. Using this approach, analytes could be identified in spiked sediment samples at concentrations down to 13-65 µg/kg dw. On-site validation experiments conducted aboard the research vessel R/V Oceania demonstrated the method's practical applicability, enabling the successful identification of four cyclic sulfur mustard degradation products at concentrations of 15-308µg/kg in sediments immediately after being collected near a wreck at the Bornholm Deep dumpsite in the Baltic Sea.

Case studies in nanny state name-calling: what can we learn?

The 'nanny state' has become a popular metaphor in debates about public health regulation. It fulfils a particular role in that debate: to caution government against taking action. This paper presents case studies of nanny state criticisms, using them to identify a series of contextual features that may assist in better understanding, evaluating and where appropriate, resisting the rhetorical force of nanny state criticisms. The case studies presented include Rush Limbaugh's reactions to Michelle Obama's efforts to encourage American food companies to market healthier food to children; Christopher Hitchens' critique of New York City Mayor Michael Bloomberg's public health policies; and the reaction of neoliberal think tanks to Australia's plain tobacco packaging legislation. These case studies do not provide a basis for making generalisations about the practice of 'nanny state name-calling'. Nor do they preclude debate about the appropriate limits of government action. However, in appropriate cases they may assist policy-makers and public health advocates to contest the framing of public health interventions as unwarranted incursions into the private lives of individuals. One important lesson from these case studies is that the principal concern of nanny state critics is not loss of freedom as such, but the role of the state. The nanny state critique is ultimately a call for the state to be agnostic about the health of citizens, allowing market forces to dominate. Although the nanny state critique is not new, it is a significant challenge to government efforts to address lifestyle-influenced risk factors for non-communicable diseases, including tobacco use, harmful use of alcohol, and unhealthy diet.

Reprint of: Food reformulation and the (neo)-liberal state: new strategies for strengthening voluntary salt reduction programs in the UK and USA.

Globally, excess salt intake is a significant cause of preventable heart disease and stroke, given the established links between high salt intake, high blood pressure, and cardiovascular disease. This paper describes and evaluates the voluntary approaches to salt reduction that operate in the United Kingdom and the United States, and proposes a new strategy for improving their performance. Drawing on developments in the theory and practice of public health governance, as well as theoretical ideas from the field of regulatory studies, this paper proposes a responsive regulatory model for managing food reformulation initiatives, including salt reduction programs. This model provides a transparent framework for guiding industry behavior, making full use of industry's willingness to participate in efforts to create healthier products, but using 'legislative scaffolding' to escalate from self-regulation towards co-regulation if industry fails to play its part in achieving national goals and targets.

Sum decomposition of Mueller-matrix images and spectra of beetle cuticles.

Spectral Mueller matrices measured at multiple angles of incidence as well as Mueller matrix images are recorded on the exoskeletons (cuticles) of the scarab beetles Cetonia aurata and Chrysina argenteola. Cetonia aurata is green whereas Chrysina argenteola is gold-colored. When illuminated with natural (unpolarized) light, both species reflect left-handed and near-circularly polarized light originating from helicoidal structures in their cuticles. These structures are referred to as circular Bragg reflectors. For both species the Mueller matrices are found to be nondiagonal depolarizers. The matrices are Cloude decomposed to a sum of non-depolarizing matrices and it is found that the cuticle optical response, in a first approximation can be described as a sum of Mueller matrices from an ideal mirror and an ideal circular polarizer with relative weights determined by the eigenvalues of the covariance matrices of the measured Mueller matrices. The spectral and image decompositions are consistent with each other. A regression-based decomposition of the spectral and image Mueller matrices is also presented whereby the basic optical components are assumed to be a mirror and a circular polarizer as suggested by the Cloude decomposition. The advantage with a regression decomposition compared to a Cloude decomposition is its better stability as the matrices in the decomposition are determined a priori. The origin of the depolarizing features are discussed but from present data it is not possible to conclude whether the two major components, the mirror and the circular polarizer are laterally separated in domains in the cuticle or if the depolarization originates from the intrinsic properties of the helicoidal structure.

Food reformulation and the (neo)-liberal state: new strategies for strengthening voluntary salt reduction programs in the UK and USA.

Globally, excess salt intake is a significant cause of preventable heart disease and stroke, given the established links between high salt intake, high blood pressure, and cardiovascular disease. This paper describes and evaluates the voluntary approaches to salt reduction that operate in the United Kingdom and the United States, and proposes a new strategy for improving their performance. Drawing on developments in the theory and practice of public health governance, as well as theoretical ideas theoretical ideas from the field of regulatory studies, this paper proposes a responsive regulatory model for managing food reformulation initiatives, including salt reduction programs. This model provides a transparent framework for guiding industry behavior, making full use of industry's willingness to participate in efforts to create healthier products, but using 'legislative scaffolding' to escalate from self-regulation towards co-regulation if industry fails to play its part in achieving national goals and targets.

Evaluation of sorbent materials for the sampling and analysis of phosphine, sulfuryl fluoride and methyl bromide in air.

Phosphine (PH3), sulfuryl fluoride (SO2F2) and methyl bromide (CH3Br) are highly toxic chemical substances commonly used for fumigation, i.e., pest control with gaseous pesticides. Residues of fumigation agents constitute a health risk for workers affected, and therefore accurate methods for air sampling and analysis are needed. In this study, three commercial adsorbent tubes; Carbosieve SIII™, Air Toxics™ and Tenax TA™, were evaluated for sampling these highly volatile chemicals in air and their subsequent analysis by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). The breakthrough volume (BTV) of each fumigant was experimentally determined on the different adsorbents at concentrations at or above their permissible exposure limits, using a method based on frontal chromatography of generated fumigant atmospheres. Carbosieve SIII™, a molecular sieve possessing a very high specific area, proved to be a better adsorbent than both Air Toxics™ and Tenax TA™, resulting in at least a 4-fold increase of the BTV50%. BTV50% for Carbosieve SIII™ at 20°C was measured as 4.7L/g, 5.5L/g and 126L/g for phosphine, sulfuryl fluoride and methyl bromide, respectively, implying safe sampling volumes of 1.9L, 2.2L and 50L, respectively, for a commercial tube packed with 800mg Carbosieve SIII™. The temperature dependence of BTV was strong for Carbosieve SIII™, showing a reduction of 3-5%/°C in breakthrough volume within the range -20 to 40°C. Furthermore, although Carbosieve SIII™ reportedly has a higher affinity for water than most other adsorbents, relative humidity had only a moderate influence on the retention capacity of phosphine. Overall, the applicability of Carbosieve SIII™ adsorbent sampling in combination with TD-GC-MS analysis was demonstrated for highly volatile fumigants.

Guided-mode resonant coherent light absorbers.

We present a new class of coherent perfect absorbers based on guided-mode resonance in thin semiconductor films. Using particle-swarm optimization methods, we design a thin-film amorphous silicon grating that maximizes coherent modulation of the absorbance. The optimized device exhibits a maximum scattering power of ∼94% and a power absorption limit approaching 100% at the 1550-nm wavelength.

Emission factors for gases and particle-bound substances produced by firing lead-free small-caliber ammunition.

Lead-free ammunition is becoming increasingly popular because of the environmental and human health issues associated with the use of leaded ammunition. However, there is a lack of data on the emissions produced by firing such ammunition. We report emission factors for toxic gases and particle-bound compounds produced by firing lead-free ammunition in a test chamber. Carbon monoxide, ammonia, and hydrogen cyanide levels within the chamber were analysed by Fourier transform infrared spectroscopy, while total suspended particles and respirable particles were determined gravimetrically. The metal content of the particulate emissions was determined and the associated organic compounds were characterized in detail using a method based on thermal desorption coupled to gas chromatography and mass spectrometry. The particulate matter (∼30 mg/round) consisted primarily of metals such as Cu, Zn, and Fe along with soot arising from incomplete combustion. Nitrogen-containing heterocyclic aromatic compounds such as carbazole, quinolone, and phenazine were responsible for some of the 25 most significant chromatographic peaks, together with PAHs, diphenylamine, and phthalates. Emission factors were determined for PAHs and oxygenated PAHs; the latter were less abundant in the gun smoke particles than in domestic dust and diesel combustion smoke. This may be due to the oxygen-deficient conditions that occur when the gun is fired. By using an electrical low pressure impactor, it was demonstrated that more than 90% of the particles produced immediately after firing the weapon had diameters of less than 30 nm, and so most of the gun smoke particles belonged to the nanoparticle regime.

Analysis of hydrogen cyanide in air in a case of attempted cyanide poisoning.

A 32-year-old man attempted to poison his ex-girlfriend with hydrogen cyanide by hiding the pesticide Uragan D2 in her car. During the police investigation, chemical analysis of the air inside the car was performed. Hydrogen cyanide was detected through on-site air analysis using a portable Fourier transform infrared (FTIR) spectroscopy gas analyzer and colorimetric gas detection tubes. Furthermore, impinger air-sampling was performed for off-site sample preparation and analysis by gas chromatography-mass spectrometry (GC-MS). All three independent techniques demonstrated the presence of hydrogen cyanide, at concentrations of 14-20 ppm. Owing to the high volatility of hydrogen cyanide, the temperature and the time since exposure have a substantial effect on the likelihood of detecting hydrogen cyanide at a crime scene. The prevailing conditions (closed space, low temperature) must have supported the preservation of HCN in the car thus enabling the identification even though the analysis was performed several days after the hydrogen cyanide source was removed. This paper demonstrates the applicability of combining on-site FTIR measurements and off-site GC-MS analysis of a crime scene in order to ensure fast detection as well as unambiguous identification for forensic purposes of hydrogen cyanide in air.

Using a legal and regulatory framework to identify and evaluate priorities for cancer prevention.

This paper presents a framework for identifying legal and regulatory interventions for the prevention of risk factors for cancer at the population level. The framework has wider application for behavioural risk factors for other non-communicable diseases. It is based on four different types of assessment: identifying the determinants of cancer and key settings for interventions; reviewing the key strategies that law can deploy; considering the most appropriate level for interventions within federal systems; and considering the role of law within a broader set of public health responses that includes voluntary standards, co-regulation, outcome-based regulation and more technical, prescriptive controls. The paper argues that law is an important tool for preventing the burden of disease from cancer. It then uses the framework to evaluate the current status of regulatory strategies for cancer prevention and to identify law reform priorities, taking Australia as a case study. The paper illustrates the application of the model at the country level by making extensive use of Australian evidence and published research. However, the methodology presented, the regulatory issues discussed, the evidence cited and the law reform priorities identified will be relevant to other countries with a substantial burden from cancer and non-communicable diseases.