Perturbations of the optical properties of mineral dust particles by mixing with black carbon: A numerical simulation study

Field observations show that individual aerosol particles are a complex mixture of a wide variety of species, reflecting different sources and physico-chemical transformations. The impacts of individual aerosol morphology and mixing characteristics on the Earth system are not yet fully understood. Here we present a sensitivity study on climate-relevant aerosols optical properties to various approximations. Based on aerosol samples collected in various geographical locations, we have observationally constrained size, morphology and mixing, and accordingly simulated, using the discrete dipole approximation model (DDSCAT), optical properties of three aerosols types: (1) bare black carbon (BC) aggregates, (2) bare mineral dust, and (3) an internal mixture of a BC aggregate laying on top of a mineral dust particle, also referred to as polluted dust. DDSCAT predicts optical properties and their spectral dependence consistently with observations for all the studied cases. Predicted values of mass absorption, scattering and extinction coefficients (MAC, MSC, MEC) for bare BC show a weak dependence on the BC aggregate size, while the asymmetry parameter (g) shows the opposite behavior. The simulated optical properties of bare mineral dust present a large variability depending on the modeled dust shape, confirming the limited range of applicability of spheroids over different types and size of mineral dust aerosols, in agreement with previous modeling studies. The polluted dust cases show a strong decrease in MAC values with the increase in dust particle size (for the same BC size) and an increase of the single scattering albedo (SSA). Furthermore, particles with a radius between 180 and 300 nm are characterized by a decrease in SSA values compared to bare dust, in agreement with field observations. This paper demonstrates that observationally constrained DDSCAT simulations allow one to better understand the variability of the measured aerosol optical properties in ambient air and to define benchmark biases due to different approximations in aerosol parametrization

Development of a new molecular typing method of Salmonella spp. based on SNPs detection

The aim of this study was to develop a new molecular typing method of Salmonella spp. based on the detection of point mutations (Single Nucleotide Polymorphisms or SNPs) in the genome. Several genomic regions (ManB, InvA, pduF) were sequenced in strains isolated from pig, the sequences were aligned and 49 point mutations were identified. A panel of 12 SNPs giving a genotype characteristic of a particular serotype was selected. Until now, thes selected SNPs were unable to distinguish the all strains. Therefore, additional SNPs must be selected

The new resilience of emerging and developing countries: systemic interlocking, currency swaps and geoeconomics

The vulnerability/resilience nexus that defined the interaction between advanced and developing economies in the post-WWII era is undergoing a fundamental transformation. Yet, most of the debate in the current literature is focusing on the structural constraints faced by the Emerging and Developing Countries (EDCs) and the lack of changes in the formal structures of global economic governance. This paper challenges this literature and its conclusions by focusing on the new conditions of systemic interlocking between advanced and emerging economies, and by analysing how large EDCs have built and are strengthening their economic resilience. We find that a significant redistribution of ‘policy space’ between advanced and emerging economies have taken place in the global economy. We also find that a number of seemingly technical currency swap agreements among EDCs have set in motion changes in the very structure of global trade and finance. These developments do not signify the end of EDCs’ vulnerability towards advanced economies. They signify however that the economic and geoeconomic implications of this vulnerability have changed in ways that constrain the options available to advanced economies and pose new challenges for the post-WWII economic order

Traçabilité dans la filière viande. I. La traçabilité administrative.

peer reviewedLe secteur de la viande a été secoué ces dernières années par quelques scandales, tels ceux des hormones et de la dioxine, avec pour conséquences une perte de confiance de la part du consommateur et une perturbation du marché de la viande. Pour redresser l’image des produits carnés belges, il est important de pouvoir en déterminer et en garantir l’origine. En Belgique, il existe divers systèmes de traçabilité administrative dont le principal est le système SANITEL qui comprend un système automatisé de traitement de données relatives à l’identification et l’enregistrement des animaux. Au-delà de l’aspect légal et réglementaire, différentes initiatives, visant une amélioration de la qualité, fleurissent : "les labels". Ceux-ci intègrent fréquemment la traçabilité dans leur cahier des charges. La traçabilité administrative n’est pas infaillible, la perte de documents et les fraudes peuvent ternir l’image de celle-ci. C’est pourquoi le système documentaire a été associé aux empreintes génétiques des animaux.

\u3cem\u3eI Love New York\u3c/em\u3e: Does New York Love Me?

This article seeks to highlight reality television’s most popular re-articulation of the Jezebel and the Sapphire stereotypes while assessing its implications for African American women. Nearly eight decades after their inception in mass mediated culture, the Jezebel and Sapphire stereotypes have been reborn in the form of Tiffany Pollard, better known as “New York,” and her mother “Sister Patterson” (respectively). Television acts as a powerful socialization agent, and thus plays a significant role in how audiences shape their racially stratified and gendered world. Researchers employed discourse analysis to provide the rich contextual data necessary to capture the effects of I Love New York; additionally, researchers will illustrate notions of patriarchy and hegemony. Further, the authors seek to provide readers with the motivation and materials to self-identify, and more importantly, self-correct

Measurements of ice nucleation by mineral dusts in the contact mode

Formation of ice in Earth\u27s atmosphere at temperatures above approximately −20 °C is one of the outstanding problems in cloud physics. Contact nucleation has been suggested as a possible mechanism for freezing at relatively high temperatures; some laboratory experiments have shown contact freezing activity at temperatures as high as −4 °C. We have investigated Arizona Test Dust and kaolinite as contact nuclei as a function of size and temperature and find that the fraction of submicron particles that are active as contact ice nuclei is less than 10−3 for −18 °C and greater. We also find that the different dusts are quite distinct in their effectiveness as contact nuclei; Arizona Test Dust catalyzed freezing in the contact mode at all mobility diameters we tested at −18 °C whereas kaolinite triggered freezing only for mobility diameters of 1000 and 500 nm at that temperature

A systematic approach in analyzing sustained oscillations in an NF-kB signal transduction pathway system

Oscillation phenomenon is very common in biological systems. It is crucial to study oscillatory behaviors to understand gene regulation functions. Model-based analysis in combination with experimental study provides a new and systematic way to investigate biological oscillations. The nuclear factor-kB (NF-kB) signaling is an important signaling pathway that is involved in a variety of cellular processes including immune response, inflammation, and apoptosis. Recent studies revealed damped oscillations of NF-kB activity both experimentally and computationally, etc. In this work, based on a differential equation model, bifurcation analysis was used to examine whether it was possible for this system to produce sustained oscillations (limit cycle oscillations) rather than damped oscillations. Both one- and two-parameter bifurcation analyses have been performed and it was found that certain conditions could possibly result in sustained oscillations of nuclear NF-kB activity. The parameter regimes corresponding to such oscillations were calculated with this method

Radiative absorption enhancements by black carbon controlled by particle-to-particle heterogeneity in composition.

Black carbon (BC) absorbs solar radiation, leading to a strong but uncertain warming effect on climate. A key challenge in modeling and quantifying BC's radiative effect on climate is predicting enhancements in light absorption that result from internal mixing between BC and other aerosol components. Modeling and laboratory studies show that BC, when mixed with other aerosol components, absorbs more strongly than pure, uncoated BC; however, some ambient observations suggest more variable and weaker absorption enhancement. We show that the lower-than-expected enhancements in ambient measurements result from a combination of two factors. First, the often used spherical, concentric core-shell approximation generally overestimates the absorption by BC. Second, and more importantly, inadequate consideration of heterogeneity in particle-to-particle composition engenders substantial overestimation in absorption by the total particle population, with greater heterogeneity associated with larger model-measurement differences. We show that accounting for these two effects-variability in per-particle composition and deviations from the core-shell approximation-reconciles absorption enhancement predictions with laboratory and field observations and resolves the apparent discrepancy. Furthermore, our consistent model framework provides a path forward for improving predictions of BC's radiative effect on climate