Copper (Cu) is naturally present in all soils with a normal range of 2 -60 mg kg 21 . The traditional use of Cu fungicides against mildew diseases has led to the accumulation of Cu in some vineyard and orchard soils. Consequently, there is a move to reduce the use of these compounds in agriculture, especially in organic cultivation. A comprehensive study has not been made of the Cu content of Greek agricultural soils, which are typically alkaline with high clay content and may, therefore, be vulnerable to Cu accumulation. Within the framework of various projects, surface soil samples were taken from 10 different regions of Greece for various representative crops, and especially, for fallow soil and abandoned land. The samples were analyzed for total (aqua regia digestion) and DTPA-extractable Cu content and for several physical and chemical properties. Mean values of total Cu for the different regions of the country ranged from 16 (Limnos and Thera) to 89 mg kg 21 (Nemea), with an overall mean of 38 + 26 mg kg 21 . Significantly lower Cu content (27 mg kg 21 ) was found for annual than for other crops. The mean values for fallow land, vines, and olives were close to the overall mean, but for citrus the mean value was slightly higher. The highest value of 70 mg kg 21 was found for orchards/nuts

The self-organizing mechanism is a universal approach that is widely followed in nature. In this work, a novel self-organizing model describing diffusion over a lattice is introduced. Simulation results for the model’s active lattice sites demonstrate an evolution curve that is very close to those describing the evolution of infected European populations by COVID-19. The model was further examined against real data regarding the COVID-19 epidemic for seven European countries (with a total population of 290 million) during the periods in which social distancing measures were imposed, namely Italy and Spain, which had an enormous spread of the disease; the successful case of Greece; and four central European countries: France, Belgium, Germany and the Netherlands. The value of the proposed model lies in its simplicity and in the fact that it is based on a universal natural mechanism, which through the presentation of an equivalent dynamical system apparently documents and provides a better understanding of the dynamical process behind viral epidemic spreads in general—even pandemics, such as in the case of COVID-19—further allowing us to come closer to controlling such situations. Finally, this model allowed the study of dynamical characteristics such as the memory effect, through the autocorrelation function, in the studied epidemiological dynamical systems.

In this brief, the spontaneous symmetry breaking (SSB) of the φ 4 theory in phase space, is studied. This phase space results from the appropriate system of Poincaré maps, produced in both the Minkowski and the Euclidean time. The importance of discretization in the creation of phase space, is highlighted. A series of interesting, novel, unknown behaviors are reported for the first time; among them the most characteristic is the change in stability. In specific, the stable fixed points of the φ 4 potential appear as unstable ones, in phase space. Additionally, in the Euclidean-time phase space a unique instability in the position of the critical point, can be created. This instability is further proposed to host tachyonic field in Euclidean space.

In present times, the largest amount of data is being controlled in a centralized manner. However, as the data are in essence the fuel of any application and service, there is a need to make the data more findable and accessible. Another problem with the data being centralized is the limited storage as well as the uncertainty of their authenticity. In the Internet of Things (IoT) sector specifically, data are the key to develop the most powerful and reliable applications. For these reasons, there is a rise on works that present decentralized marketplaces for IoT data with many of them exploiting blockchain technology to offer security advantages. The main contribution of this work is to review the existing works on decentralized IoT data marketplaces and discuss important design aspects and options so as to guide (a) the prospective user to select the IoT data marketplace that matches their needs and (b) the potential designer of a new marketplace to make insightful decisions.

The influence of cultivation practice on the fertility of volcanic soils on Santorini, an important wine-producing area of Greece, has been examined. In conventional agriculture, weed control, typically of N-fixing species, is carried out using herbicides, whereas in organic practice it is achieved though plowing, leaving the soil vulnerable to erosion. Soil samples were taken from conventionally and organically cultivated vines and tomatoes and from abandoned vineyards at five locations. Biological indicators of soil quality were measured in addition to physicochemical properties. The loam sandy soils had an acid to slightly alkaline pH reaction, with low organic matter. Earthworms (Lumbricidae) were not found. Enchytreids were absent from conventional soils but were found in low abundance in organic and abandoned vineyard systems. Enzyme activity showed no dependence on cultivation systems but was low compared with other Greek soils. Organic practices adopted on Santorini have maintained soil fertility in the short term.