Spatio-temporal Event Studies for Air Quality Assessment under Cross-sectional Dependence

Event Studies (ES) are statistical tools that assess whether a particular event of interest has caused changes in the level of one or more relevant time series. We are interested in ES applied to multivariate time series characterized by high spatial (cross-sectional) and temporal dependence. We pursue two goals. First, we propose to extend the existing taxonomy on ES, mainly deriving from the financial field, by generalizing the underlying statistical concepts and then adapting them to the time series analysis of airborne pollutant concentrations. Second, we address the spatial cross-sectional dependence by adopting a twofold adjustment. Initially, we use a linear mixed spatio-temporal regression model (HDGM) to estimate the relationship between the response variable and a set of exogenous factors, while accounting for the spatio-temporal dynamics of the observations. Later, we apply a set of sixteen ES test statistics, both parametric and nonparametric, some of which directly adjusted for cross-sectional dependence. We apply ES to evaluate the impact on NO2 concentrations generated by the lockdown restrictions adopted in the Lombardy region (Italy) during the COVID-19 pandemic in 2020. The HDGM model distinctly reveals the level shift caused by the event of interest, while reducing the volatility and isolating the spatial dependence of the data. Moreover, all the test statistics unanimously suggest that the lockdown restrictions generated significant reductions in the average NO2 concentrations

Synthesis and characterization of a 2-periodic cadmium-based metal-organic framework: A study on reversible water adsorption

A previously-reported cadmium-based two-periodic metal-organic framework [Cd1.5(BTC)(H2O)4.5]n⋅nH2O (CP1) has been re-synthesized, where H3BTC ¼ 1,3,5-benzenetricarboxylic acid. CP1 was characterized with single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD) followed by various thermal analyses such as thermogravimetric analysis (TGA), hot stage microscopy (HSM) and differential scanning calorimetry (DSC). CP1 is composed of 2-periodic layers, which are interdigitated. Heating can effectively remove the uncoordinated and coordinated water molecules resulting in an amorphous product CP1′. The original framework can be regenerated by readsorption of water from the atmosphere, indicating that the dehydration is reversibl

Exploiting the Reducing Properties of Lignin for the Development of an Effective Lignin@Cu2O Pesticide

Lignin is a natural polymer produced in huge amounts by the paper industry. Innovative applications of lignin, especially in agriculture, represent a valuable way to develop a more sustainable economy. Its antioxidant and antimicrobial properties, combined with its biodegradability, make it particularly attractive for the development of plant protection products. Copper is an element that has long been used as a pesticide in agriculture. Despite its recognized antimicrobial activity, the concerns derived from its negative environmental impact is forcing research to move toward the development of more effective and sustainable copper-based pesticides. Here a simple and sustainable way of synthesizing a new hybrid material composed of Cu2O nanocrystals embedded into lignin, named Lignin@Cu2O is presented. The formation of cuprite nanocrystals leaves the biopolymer intact, as evidenced by infrared spectroscopy, gel permeation chromatography, and Pyrolysis-GC analysis. The combined activity of lignin and cuprite make Lignin@Cu2O effective against Listeria monocytogenes and Rhizoctonia solani at low copper dosage, as evidenced by in vitro and in vivo tests conducted on tomato plants

Investigation of antibacterial activity of new classes of essential oils derivatives

Essential oils (EOs) have deserved much attention in the past decades for their antimicrobial activity, since many of them have demonstrated efficacy against food-borne pathogenic and spoilage microorganisms. Moreover, they have potential application in animal nutrition as multifunctional feed supplements, avoiding or diminishing the use of antibiotics in livestock. However, low solubility and bioavailability as well as volatility and marked aromatic note are important limitations in food and feed applications. In this study we present the synthesis, characterization and evaluation of the antibacterial activity of new thymol, carvacrol and menthol derivatives. The new compounds have been designed to overcome the limitations of the precursors, such as poor water solubility and volatility, still maintaining a good antimicrobial profile. We evaluated the activity of the synthetized compounds against pathogens causing important foodborne diseases, . i.e. . Clostridium perfringens, . Salmonella typhimurium, . Salmonella enteritidis and . Escherichia coli. The low MICs and MBCs values for some of the studied compounds, combined with water solubility and negligible cytotoxicity towards HT-29 human cells, confirmed the potential use for EOs derivatives in the food industry

Fabricating organometallic wheel-and-axle compounds for the creation of dynamically porous crystalline materials

A family of organometallic compounds has been designed based on half-sandwich ruthenium complexes [(arene)Ru(L)X2] (X=Cl, I); this showed dynamic host-guest properties towards volatile molecules, caused by small local reversible structural rearrangements. These features derive from the supramolecular organization of the compounds in the solid state, based on a so-called wheel-and-axle pattern, that is known to favour guest inclusion. The molecular features of the Ru complexes (arene size and shape, ligand size and chemical properties, halogen nature) were screened in order to optimize the final performances of the materials. The design strategy has proven to be succesful, affording materials capable to dynamically exchange volatile molecules by gas-solid processes and solid-solid transformations without loss of crystallinity

Organometallic chemistry meets crystal engineering to give responsive crystalline materials

Dynamically porous crystalline materials have been obtained by engineering organometallic molecules. This feature article deals with organometallic wheel-and-axle compounds, molecules with two relatively bulky groups (wheels) connected by a linear spacer. The wheels are represented by half-sandwich Ru(II) moieties, while the spacer can be covalent or supramolecular in character. Covalent spacers are obtained using divergent bidentate ligands connecting two [(arene) RuX2] groups. Supramolecular spacers are instead obtained by exploiting the dimerization of COOH or C(O)NH2 groups appended to N-based ligands. A careful choice of ligand functional groups and X ligands leads to the isolation of crystalline materials with remarkable host-guest properties, evidenced by the possibility of reversibly capturing/releasing volatile guests through heterogenous solid-gas reactions. Structural correlations between the crystalline arrangement of the apohost and the host-guest compounds allow us to envisage the structural path followed by the system during the exchange processes

Crystal engineering of flexible metallorganic supramolecular networks

Flexibly porous crystalline materials have been obtained by engineering the structure of metal-containing molecules. In particular, the review deals with 'wheel-and-axle' compounds, molecules with two bulky and relatively rigid end groups (wheels) that are connected by a linear rigid link (axle). Owing to their irregular shape, 'wheel-and-axle' compounds do not pack efficiently, and for this reason they tend to form inclusion compounds. Here, we present the results obtained by using metal-containing 'wheel-and-axle' complexes, where metal ions are inserted in the axle or in the wheels. In particular, wheel-and-axle diols are obtained by inserting Pd(II) and Pt(II) ions into the axle, while metallorganic wheel-and-axle compounds are realized by using half-sandwich Ru(II) building units. A careful choice of metal coordination geometry and ligand functional groups leads to the isolation of crystalline materials with remarkable host-guest properties. Moreover, a close analysis of the crystal structures allows one to propose a model for guest uptake/release