EVA-Layered Double Hydroxide (Nano)Composites: Mechanism of Fire Retardancy

Composites of ethyleneevinyl acetate copolymer with two different layered double hydroxides have been obtained by melt blending and these have been characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, thermogravimetric analysis connected to mass spectroscopy and cone calorimetry. There is some small difference in dispersion between the zinc-containing and the magnesium-containing layered double hydroxides in EVA, but both these are microcomposites with good dispersion at the micrometer level and relatively poor dispersion at the nanometer level. There is a good reduction in the peak heat release rate at 10% LDH loading. In addition to chain stripping, which involves the simultaneous loss of both acetate and a hydrogen atom, forming acetic acid, and the formation of poly(ethylene-co-acetylene), side chain fragmentation of the acetate group also occurs and may be the dominant pathway of thermal degradation in the first step. The presence of the LDH causes acetone, rather than acetic acid, to be evolved in the initial step of the degradation

Polymer Nanocomposites Using Zinc Aluminum and Magnesium Aluminum Oleate Layered Double Hydroxides: Effects of LDH Divalent Metals on Dispersion, Thermal, Mechanical and Fire Performance in Various Polymers

Oleate-containing layered double hydroxides of zinc aluminum (ZnAl) and magnesium aluminum (MgAl) were used to prepare nanocomposites of polyethylene, poly(ethylene-co-butyl acrylate) and poly(methyl methacrylate). The additives and/or their polymer composites were characterized by X-ray diffraction, FTIR, elemental analysis, thermogravimetric analysis, mechanical testing, and cone calorimetry. The unusual packing of the monounsaturated oleate anions in the gallery of these LDHs facilitates the dispersion of these nanomaterials. The inorganic LDH protects the polymer from thermal oxidation, shown by enhancement of the thermal and fire properties of the corresponding polymer nanocomposites. There is a qualitative difference in the morphology of the two LDHs in PE and PMMA. ZnAl is better dispersed in PE while MgAl is better dispersed in PMMA. The zinc-containing material led to a large reduction in the peak heat release rate in polyethylene, while the magnesium-containing material led to enhancement of the fire properties of the more polar poly(methyl methacrylate). These fire properties are consistent with the morphological differences. Neither of these LDHs shows efficacy with poly(ethylene-co-butyl acrylate), which indicates a selective interaction between the LDH and the various polymers

Material properties of nanoclay PVC composites

Nanocomposites of poly(vinyl chloride) have been prepared using both hectorite- and bentonite-based organically-modified clays. The organic modification used is tallow-triethanol-ammonium ion. The morphology of the systems was investigated using X-ray diffraction and transmission electron microscopy and these systems show that true nanocomposites, both intercalated and exfoliated systems, are produced. The mechanical properties have been evaluated and the modulus increases upon nanocomposite formation without a significant decrease in tensile strength or elongation at break. Thermal analysis studies using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis were conducted. Thermal stability of the PVC systems was assessed using a standard thermal process evaluating the evolution of hydrogen chloride and by color development through the yellowness index. Cone calorimetry was used to measure the fire properties and especially to evaluate smoke evolution. The addition of an appropriately-modified bentonite or hectorite nanoclay leads to both a reduction in the total smoke that is evolved, and an increase in the length of time over which smoke is evolved. Along with this, a reduction in the peak heat release rate is seen. It is likely that the presence of the clay in some way interferes with the cyclization of the conjugated system formed upon HCl loss

Complex molecular relationship between vegetative compatibility groups (VCGs) in Verticillium dahliae: VCGs do not always align with clonal lineages

Verticillium wilts caused by the soilborne fungus Verticillium dahliae are among the most challenging diseases to control. Populations of this pathogen have been traditionally studied by means of vegetative compatibility groups (VCGs) under the assumption that VCGs comprise genetically related isolates that correlate with clonal lineages. We aimed to resolve the phylogenetic relationships among VCGs and their subgroups based on sequences of the intergenic spacer region (IGS) of the ribosomal DNA and six anonymous polymorphic sequences containing single-nucleotide polymorphisms (VdSNPs). A collection of 68 V dahliae isolates representing the main VCGs and subgroups (VCGs 1A, 1B, 2A, 2B, 3, 4A, 4B, and 6) from different geographic origins and hosts was analyzed using the seven DNA regions. Maximum parsimony (MP) phylogenies inferred from IGS and VdSNP sequences showed five and six distinct clades, respectively. Phylogenetic analyses of individual and combined data sets indicated that certain VCG subgroups (e.g., VCGs 1A and 1B) are closely related and share a common ancestor; however, other subgroups (e.g., VCG 4B) are more closely related to members of a different VCG (e.g., VCG 2A) than to subgroups of the same VCG (VCG 4B). Furthermore, MP analyses indicated that VCG 2B is polyphyletic, with isolates placed in at least three distinct phylogenetic lineages based on IGS sequences and two lineages based on VdSNP sequences. Results from our study suggest the existence of main VCG lineages that contain VCGs 1A and 1B; VCGs 2A and 4B; and VCG 4A, for which both phylogenies agree; and the existence of other VCGs or VCG subgroups that seem to be genetically heterogeneous or show discrepancies in their phylogenetic placement: VCG 2B, VCG 3, and VCG 6. These results raise important caveats regarding the interpretation of VCG analyses: genetic homogeneity and close evolutionary relationship between members of a VCG should not be assumed.This research was partially funded by the Sarah Chinn Kalser Faculty Research Assistance Endowment, College of Agricultural Sciences, The Pennsylvania State University. We thank all suppliers of V. dahliae isolates; J. Yanez, S. Colihan, C. Barrett, C. Black, and C. Olivares-Garcia for excellent technical support; and D. Geiser for helpful discussions during the preparation of this manuscript.Jiménez Gasco, MDM.; Malcolm, GM.; Berbegal Martinez, M.; Armengol Fortí, J.; Jimenez Diaz, R. (2014). Complex molecular relationship between vegetative compatibility groups (VCGs) in Verticillium dahliae: VCGs do not always align with clonal lineages. Phytopathology. 104(6):650-659. doi:10.1094/PHYTO-07-13-0180-RS650659104

Short communication. Soil development mediated by traditional practices shape the stand structure of Spanish juniper woodland

Producción CientíficaAim of study: Assessing the effect of soil development on the stand structure of a Spanish juniper forest traditionally shaped by livestock browsing and wood extraction. Area of study: Berlanga de Duero (Soria, Castilla y León), Spain. Material and Methods: A stand inventory served to record stand structure. Tree age, height, DBH, basal area, and overbark volume were determined in each plot. Results were pooled considering two well-differentiated degrees of soil evolution. One-way ANOVAs (and Tukey’s test) and regressions between growth parameters were performed to assess significant differences between growth performances on both types of soils. Research highlights: Deeper soils yielded significant higher plant density and stand stock figures than stony shallower profiles despite the intense past livestock activity in the area; and single tree-size was also significantly greater. Non-significant differences were found for merchantable junipers age (≈120-160 years). Wood extraction and livestock browsing should be limited on shallower soils to allow soil and forest evolution; as well as to preserve the genetic pool better adapted to hardest growing conditions

Effects of the 2021 La Palma volcanic eruption on groundwater resources (part II): Hydrochemical impacts

Volcanic eruptions can have significant implications for the management and sustainability of water resources in volcanic islands. The recent 2021 eruption of the Tajogaite volcano in La Palma Island (Canary Islands, Spain) raised concerns regarding its potential impact on groundwater resources. This study is the second part of a series investigating the hydrogeochemical impacts of the eruption. The study involved conducting three groundwater sampling campaigns during the eruption and two after the eruption, six months and one year after the eruption ceased. A total of 15 monitored points, including piezometers, wells, water galleries, and main gully collector of the island, all relatively close (2–15 km) to the erupted volcano, were sampled for the analysis of major, minor, and trace elements, physiochemical parameters, which were measured on-site. Statistical analyses were performed to assess the differences in groundwater composition before, during, and after the eruption. To evaluate the differences in water quality compared to pre-eruption events, 33 additional historical groundwater samples provided by the local Water Authority were assessed, and 103 groundwater analysis results from the groundwater data base of the Spanish National Geological Survey (IGME) were considered. The results of the study showed low but statistically significant changes in pH, T, conductivity and groundwater composition, mainly related to the high increases in several trace element concentrations, such as Al, Cr, Fe, Mo, Ni, Sr, Th, Tl, V, Zn, Ba, Cd, Co, Cu, Pb and U, with increments in various orders of magnitude for several elements. This increase was found to be highly influenced by the sample distance to the volcano during the eruption stage. The significance of these findings lies in their usefulness to enhance our understanding of the effects of volcanic eruptions on groundwater quality resources and demonstrate their resilience to this hazardous phenomenon, which ultimately underscores their reliability

Childhood trauma: methods for the identification of physeal fractures in non-adult skeletal remains

Objectives Today, fractures at the growth plate (or physis) are common injuries in children, but provide challenges of identification in skeletonized remains. Clinical studies provide detailed information on the mechanisms, locations, age of occurrence, and complications associated with physeal fractures, enabling the development of new criteria for identifying this injury in non-adults. To test these criteria, skeletal remains from five rural and urban medieval cemeteries were examined. Methods The sample consisted of 961 skeletons (0-17 years) with open epiphyses. Macroscopic observation looked for any irregularities of the metaphysis or epiphysis which was consistent with the clinical appearance of physeal fractures or resulting complications. Radiographic examination was applied to identify fracture lines or early growth arrest. Results This study revealed 12 cases of physeal trauma (1.2%). Physeal fractures occurred predominantly at the distal end (75%), and while they were identified in all age categories, they were most frequent in those aged 12-17 years (0.2% TPR). The humerus was the most commonly affected location (3/12 or 25%). Conclusions This study highlights the potential for recognizing physeal fractures in children of all ages, enhancing our understanding of non-adult trauma, and enabling us to assign a more precise age of the injury to build up a picture of their activities in the past

Management of Soil-Borne Diseases of Grain Legumes Through Broad-Spectrum Actinomycetes Having Plant Growth-Promoting and Biocontrol Traits

Chickpea (Cicer arietinum L.) and pigeonpea (Cajanus cajan L.) are the two important grain legumes grown extensively in the semiarid tropics (SAT) of the world, where soils are poor in nutrients and receive inadequate/erratic rainfall. SAT regions are commonly found in Africa, Australia, and South Asia. Chickpea and pigeonpea suffer from about 38 pathogens that cause soil-borne diseases including wilt, collar rot, dry root rot, damping off, stem canker, and Ascochyta/Phytophthora blight, and of which three of them, wilt, collar rot, and dry root rot, are important in SAT regions. Management of these soil-borne diseases are hard, as no one control measure is completely effective. Advanced/delayed sowing date, solarization of soil, and use of fungicides are some of the control measures usually employed for these diseases but with little success. The use of disease-resistant cultivar is the best efficient and economical control measure, but it is not available for most of the soil-borne diseases. Biocontrol of soil-borne plant pathogens has been managed using antagonistic actinobacteria, bacteria, and fungi. Actinobacterial strains of Streptomyces, Amycolatopsis, Micromonospora, Frankia, and Nocardia were reported to exert effective control on soil-borne pathogens and help the host plants to mobilize and acquire macro- and micronutrients. Such novel actinomycetes with wide range of plant growth-promoting (PGP) and antagonistic traits need to be exploited for sustainable agriculture. This chapter gives a comprehensive analysis of important soil-borne diseases of chickpea and pigeonpea and how broad-spectrum actinomycetes, particularly Streptomyces spp., could be exploited for managing them