A mechanistic spatio-temporal modeling of COVID-19 data

Understanding the evolution of an epidemic is essential to implement timely and efficient preventive measures. The availability of epidemiological data at a fine spatio-temporal scale is both novel and highly useful in this regard. Indeed, having geocoded data at the case level opens the door to analyze the spread of the disease on an individual basis, allowing the detection of specific outbreaks or, in general, of some interactions between cases that are not observable if aggregated data are used. Point processes are the natural tool to perform such analyses. We analyze a spatio-temporal point pattern of Coronavirus disease 2019 (COVID-19) cases detected in Valencia (Spain) during the first 11 months (February 2020 to January 2021) of the pandemic. In particular, we propose a mechanistic spatio-temporal model for the first-order intensity function of the point process. This model includes separate estimates of the overall temporal and spatial intensities of the model and a spatio-temporal interaction term. For the latter, while similar studies have considered different forms of this term solely based on the physical distances between the events, we have also incorporated mobility data to better capture the characteristics of human populations. The results suggest that there has only been a mild level of spatio-temporal interaction between cases in the study area, which to a large extent corresponds to people living in the same residential location. Extending our proposed model to larger areas could help us gain knowledge on the propagation of COVID-19 across cities with high mobility levels.     

Gathered fruits and cultivated plants at Bercy (Paris), a Neolithic village in a fluvial context

Recent rescue excavations at Bercy (Paris), a site on the alluvial plain of the Seine valley, yielded plant remains which are associated with the recent occupation phase dating from the middle Neolithic II (Chasséen), when a village was established on the former channel of the river Seine. Various contexts (the channel, the flat lower part of the bank, and several archaeological features) have been studied and 84 taxa have been identified. Cultivated plants are represented by Triticum aestivum/durum, T. dicoccum, T. monococcum and Hordeum vulgare. Among the wild plants with potentially edible fruits or seeds, only very few satisfy the various criteria for association with human activities: Corylus avellana, Vitis sylvestris, Cornus sanguinea, Quercus sp. and Prunus spinosa of which carbonized fruits were also present, were found in archaeological features and were very abundant. Though not found in archaeological features, we consider that Crataegus monogyna (carbonized and well represented) and Rubus spp. (especially abundant) were not deposited there naturally and had also been intentionally collected. Finally, it is suggested that the allochthonous (varied) origin of these taxa is the reason why there are no concentrations of their fruits in the channel. The exploitation of wild seeds and fruits appears to have been very selective. All other wild taxa can be attributed to natural deposition.     

Adaptation of wastewater surface flow wetland formulae for application in constructed stormwater wetlands

Over the past 30 years, the use of constructed wetlands for wastewater treatment has been a topic of significant research culminating in a good data base from which simplistic equations have been derived to aid in the design of these facilities to meet long term water quality treatment performance criteria. Over the past decade, the use of treatment wetlands has extended to stormwater and combined sewer overflow (CSO) management applications. Designing constructed wetlands for stormwater and CSO applications have unique challenges stemming from the highly stochastic nature of the hydraulic and pollutant loading on a stormwater wetland compared with wastewater treatment systems. This paper explores the possibility of adapting the simplistic models for wastewater wetlands for interim use in developing design guidelines for stormwater wetland systems. A procedure that takes into account the unsteady intermittent nature of stormwater inflows to these wetlands has been incorporated into one of these simplistic models and a case study presented to demonstrate the application of the procedure.     

The Høylandet area – patterns and processes of a pristine boreal-subalpine ecosystem – a synopsis

The research activities on soil–freshwaterinteractions and freshwater biotic structure andprocesses in the Høylandet area during the years 1986–89are presented in this issue ofHydrobiologia. The 9 papers cover a range of topicsfrom physiochemical gradients and processes in soilsand freshwaters to selected aspects of freshwaterbiotic community structure and temporal variability.This synopsis aims (a) to present an overview of majorfindings, (b) to interpret the results in the contextof air pollution effects and (c) to outlinesuggestions for future research activities inHøylandet. The area has a sub-oceanic climate varyingfrom 1100 to 2200 mm of precipitation normallyoriginating from unpolluted airmasses from the NorthAtlantic. It is chemically dominated by sea salts, haslow concentrations and low deposition of mineralacids. The catchment geology is variable and complexand consists mainly of various granites and gneisses.The soils are undisturbed ancient soils,primarily iron podzols associated with forests, orintact histosols with strong organic characterassociated with mires, often quite acidic.They are sensitive because occurrence of predominantlyinsoluble unstable Al-complexes may leach out ifexposed to anthropogenically acidified soil drainagewater and turn up as toxic inorganic aqueous Al insurface runoff. Small amounts of locally generatednitrogen compounds are mostly retained in thecatchment. The water qualities of these Høylandetsites are run by inputs of sea salts, hydrologicalprocesses including dilution of the base flow, orlateral surface or overland flow and in-catchmentprocesses. Relative to affected areas, it appears thatthe inputs and catchment processes are in balance,i.e., that the inputs of strong acid anions, hydrogenions and sea salts are equilibrated by internalweathering and other processes and integrated withinapparently intact biogeochemical cycles. The overallresult is that these soils remain a net source ofalkalinity to the runoff. These results are confirmedby regional studies of water quality both at low andhigh flow which show that the humus and ionic contentof the water decreased with elevation, headwatersbeing more dominated by sea salts and dilutionprocesses. Excess sulphate concentrations are low, andfew if any sites appear anthropogenically acidified,the most acid pHs reflecting presence of natural weakorganic acids.The resulting surface water quality allows a diverseaquatic fauna and flora with representatives of manyacid-sensitive groups. The fish fauna consists ofself-reproducing salmonid populations with normaldemography and ecological interactions. Despite highin-lake mortality, both brown trout and Arctic charrexhibited normal age-class compositions, with noindication of the recruitment failure or highpost-spawning mortality commonly observed inacid-stressed situations. The zooplankton and benthos in the lakesare inhabited by populations of several acid sensitivespecies, like Daphnia spp and Gammaruslacustris, and with dominance of mayfly species ofthe genus Baetis in the stream fauna. Thediatom flora includes many species which are rare orabsent in acidified waters. The observed gradients indiversity and biomass seem dominated by localenvironmental conditions which reflect natural ratherthan man-made processes. The pristine nature of thearea also emerges from the paleoecological studies inLake Røyrtjønna which show that the low acidity ofthis lake evironment has persisted from preindustrialtill present times. Suggestion for future researchactivities in Høylandet are outlined.     

Sexual dimorphism of motorneurons: Timbal muscle innervation in male periodical cicadas and homologous structures in females

Summary Treatment of cultured goldfish xanthophores by hormone (ACTH) or c-AMP induces not only pigment dispersion, but subsequent outgrowth of processes, and pigment translocation into these processes. These latter effects are shown to proceed as follows: First the edge of the cytoplasmic lamellae takes on a scalloped contour with numerous protrusions. These presumably serve as nucleation centers where short microfilament bundles are assembled, Later, the microfilament bundles elongate (grow), often resulting in an extension of the protrusions to become filopodia while the proximal end of the microfilaments penetrates into the thicker portion of the cellular process which now houses the pigment, i.e., the carotenoid droplets. Carotenoid droplets appear to migrate along the microfilament bundles, or cytoplasmic channels associated with them, into the filopodia. Finally, some of the filopodia become broader, thicker and laden with carotenoid droplets and are then recognized by light microscopy as pigmented cellular processes. The microfilaments have been shown to be actin filaments by their thickness, the size of their subunits, and decoration by heavy meromyosin. Evidence is presented which suggests that the growth of these actin filaments may come about by recruitment from short F-actin strands found in random orientation in adjacent areas.     

A systematic approach to the simulation of short-term processes in the plant-environment complex

Abstract. A conceptual framework is presented for modelling short-term processes in the plant and its environment as an integrated system. Flows of water, water vapour, heat, momentum, CO₂, soluble carbohydrate and phosphorus are all described by equations of the same general type, i.e. in terms of diffusivity-type parameters, capacities and potential gradients. A representative volume of the crop is divided horizontally into layers and vertically between crop and environment for treatment by a finite-difference method. Vertical flow occurs in the atmosphere, soil, stems and larger roots, andilateral flow between leaves and air, and between finer roots and soil. The interception of direct sunlight and the flux densities of downward and upward diffuse radiation within layers are calculated by a step-wise procedure.
The conversions of materials within the plant are treated as functions of appropriate state variables. Schemes for carbon and phosphorus provide for flow to and from the translocation system, and for photosynthesis, respiration and growth.
A model of a fully-established lucerne crop is described and the sensitivity of model performance to changes in a number of parameter values explored. Simulation runs under varying conditions indicate realistic prediction of diurnal trends.     

Gynandromorphs of the pycnogonid Anoplodactylus portus

A large sample of the pycriogonid Anoplodactylus portus , collected from the Pacific side of the Panama Canal Zone, contains a high percentage of gynandromorphs. The literature on aquatic arthropod gynandromorphs is outlined. The nature and variations of the sexual mosaic population are described and discussed. The several morphological differences between normal and mosaic members of the population are illustrated, and the possible origin of these gynandromorphs is discussed.     

Chemical mobility and bioavailabity of sediment-bound heavy metals influenced by salinity

The transfer of metals from contaminated sediments to algal cell walls (Scenedesmus quadricauda) and organisms from various trophic levels (euryhaline osmoconform hydroid Cordylophora caspia and algae Brachiomonas submarina) was studied with a multichamber device. The system consists of a central chamber which contained the mud suspension and six external chambers containing the different biological indicators. The solids in the central and external chambers are separated by 0.45 m-diameter membranes which allow diffusion of the mobilized, dissolved metal compounds. Experiments were performed with dredged sediments at various salinities (0.5, 1.0, 1.5, and 2.0 percent, respectively) and the kinetic of re-adsorption was obtained by taking samples after different time intervals. High enrichment of Cd was found in the living alga Brachiomonas submarina, but on the other side only a weak influence of salinity on re-adsorption could be observed. Model experiments with ionic Cd showed a clear dependency on Cd-sorption on the algae, Cd-concentration in solution, and salinity. These results indicate that the transfer of metals mainly depends on the specific surface properties of the substrates and on the specific chemical form of the dissolved mobilized metal.     

Stir-up effect of wind on a more-or-less stratified shallow lake phytoplankton community,Lake Balaton,Hungary

Microstratification of phytoplankton in the large shallow Lake Balaton (Hungary) was studied during a 24 h period. Dissolved O₂ showed biological stratification; flagellates exhibited a definite circadian rhythm. In the middle of the investigation a heavy storm broke out which was followed by the disappearance of differences between different layers of water. Storm-induced destratification is described by cluster-analysis. Abundances of dominant species changed differently in connection with the storm. Numbers of Nitzschia sp. increased due to stirring up from the sediment surface. Numbers of single-celled or colony-forming species (Cyclotella comta, Crucigenia quadrata, Coelosphaerium kuetzingianum) practically did not change. Numbers of all the three dominant filamentous species (Aphanizomenon fos-aquae f. klebahnii, Lyngbya limnetica, Planctonema lauterbornii) significantly decreased, which might be attributed to an unknown loss process and was followed by a competitive displacement by algae of small cell size.