Karst environments are characterized by distinctive landforms related to dissolution and a dominant subsurface drainage. The direct connection between the surface and the underlying high permeability ...aquifers makes karst aquifers extremely vulnerable to pollution. A high percentage of the world population depends on these water resources. Moreover, karst terrains, frequently underlain by cavernous carbonate and/or evaporite rocks, may be affected by severe ground instability problems. Impacts and hazards associated with karst are rapidly increasing as development expands upon these areas without proper planning taking into account the peculiarities of these environments. This has led to an escalation of karst-related environmental and engineering problems such as sinkholes, floods involving highly transmissive aquifers, and landslides developed on rocks weakened by karstification. The environmental fragility of karst settings, together with their endemic hazardous processes, have received an increasing attention from the scientific community in the last decades. Concurrently, the interest of planners and decision-makers on a safe and sustainable management of karst lands is also growing. This work reviews the main natural and human-induced hazards characteristic of karst environments, with specific focus on sinkholes, floods and slope movements, and summarizes the main outcomes reached by karst scientists regarding the assessment of environmental impacts and their mitigation.
Natural and anthropogenic caves may represent a potential hazard for the built environment, due to the occurrence of instability within caves, that may propagate upward and eventually reach the ...ground surface, inducing the occurrence of sinkholes. In particular, when caves are at shallow depth, the effects at the ground surface may be extremely severe. Apulia region (southern Italy) hosts many sites where hazard associated with sinkholes is very serious due to presence of both natural karst caves and anthropogenic cavities, the latter being mostly represented by underground quarries. The Pliocene–Pleistocene calcarenite (a typical soft rock) was extensively quarried underground, by digging long and complex networks of tunnels. With time, these underground activities have progressively been abandoned and their memory lost, so that many Apulian towns are nowadays located just above the caves, due to urban expansion in the last decades. Therefore, a remarkable risk exists for society, which should not be left uninvestigated.
The present contribution deals with the analysis of the most representative failure mechanisms observed in the field for such underground instability processes and the factors that seem to influence the processes, as for example those causing weathering of the rock and the consequent degradation of its physical and mechanical properties. Aimed at exploring the progression of instability of the cavities, numerical analyses have been developed by using both the finite element method for geological settings represented by continuous soft rock mass, and the distinct element method for jointed rock mass conditions. Both the effects of local instability processes occurring underground and the effects of the progressive enlargement of the caves on the overall stability of the rock mass have been investigated, along with the consequent failure mechanisms. In particular, degradation processes of the rock mass, as a consequence of wetting and weathering phenomena in the areas surrounding the caves, have been simulated. The results obtained from the numerical simulations have then been compared with what has been observed during field surveys and a satisfactory agreement between the numerical simulations and the instability processes, as detected in situ, has been noticed.
► Upward propagation of underground instability cause sinkholes at the surface. ► Many towns in Apulia, southern Italy, are at risk because of underground cavities. ► Progression of instability within cavities is modelled by numerical analyses. ► Underground failure mechanisms need to be identified before numerical modelling. ► Factors leading to underground failures are analyzed and modelled.
Rationnel La Société Francophone du Diabète a émis des recommandations en juin 2012 sur la prise en charge de la femme enceinte diabétique (hors diabète gestationnel). L’objectif de notre travail ...était d’évaluer les pratiques professionnelles des diabétologues depuis la parution de ces recommandations. Patients et méthodes Nous avons rétrospectivement inclus toutes les femmes diabétiques enceintes entre le 1er janvier et le 31 décembre 2013 ayant accouché au CHU. Nous avons recueilli les données suivantes : le type de diabète, la notion de grossesse programmée, les traitements prescrits tels que antidiabétiques oraux (ADO), insulines et leur mode d’administration, acide folique ainsi que les valeurs d’HbA1c pré et post-conceptionnelles. Résultats Vingt six femmes d’âge moyen 30,5 ans ont été inclus dans l’étude, 70 % d’entre elles présentant un diabète de type I. La notion de grossesse programmée est retrouvée chez 35 % des patientes, celles-ci présentant alors une valeur moyenne d’HbA1c plus faible que lors d’une grossesse non anticipée (6,7 vs 7,6 %). Deux patientes ont reçu des ADO stoppés dès la découverte de la grossesse, 24 étaient traitées par insuline délivrée par multi-injections (38 %) ou par pompes externes (62 %). Deux femmes ont été traitées par glulisine. La trace d’une supplémentation en acide folique a été retrouvée dans deux dossiers seulement. Conclusion Notre travail montre que la prise en charge thérapeutique globale des femmes enceintes diabétiques n’est pas toujours conforme aux recommandations. Des améliorations doivent être apportées concernant l’information des femmes diabétiques pour programmer leur grossesse et la valeur cible d’HbA1c à atteindre avant de concevoir (6,5 %). La prescription d’acide folique doit être plus fréquente. Les types d’insuline recommandés sont globalement connus et respectés par les prescripteurs. Déclaration d’intérêt Les auteurs déclarent ne pas avoir d’intérêt direct ou indirect (financier ou en nature) avec un organisme privé, industriel ou commercial en relation avec le sujet présenté.
An exact explicit expression is derived for the Sommerfeld integral describing the surface transverse magnetic field generated by an infinite line source placed on a plane air–earth boundary. The ...spatial distribution of the transverse magnetic field is given in series form, as a linear combination of exponential functions. The accuracy and convergence rate of the proposed formulation are investigated through numerical simulations.
•Land cover should not be considered as a static parameter in susceptibility analysis.•Changes in land cover pattern lead to modification in landslide spatial probability.•Simulated land cover ...scenarios for assessing future landslide susceptibility.•Information obtained can be helpful for land management and planning actions.
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Land cover is one of the most important conditioning factors in landslide susceptibility analysis. Usually it is considered as a static factor, but it has proven to be dynamic, with changes occurring even in few decades. In this work the influence of land cover changes on landslide susceptibility are analyzed for the past and for future scenarios. For the application, an area representative of the hilly-low mountain sectors of the Italian Southern Apennines was chosen (Rivo basin, in Molise Region). With this purpose landslide inventories and land cover maps were produced for the years 1954, 1981 and 2007. Two alternative future scenarios were created for 2050, one which follows the past trend (2050-trend), and another one more extreme, foreseeing a decrease of forested and cultivated areas (2050-alternative). The landslide susceptibility analysis was performed using the Spatial Multi-Criteria Evaluation method for different time steps, investigating changes to susceptibility over time.
The results show that environmental dynamics, such as land cover change, affect slope stability in time. In fact there is a decrease of susceptibility in the past and in the future 2050-trend scenario. This is due to the increase of forest or cultivated areas, that is probably determined by a better land management, water and soil control respect to other land cover types such as shrubland, pasture or bareland. Conversely the results revealed by the alternative scenario (2050-alternative), show how the decrease in forest and cultivated areas leads to an increase in landslide susceptibility. This can be related to the assumed worst climatic condition leading to a minor agricultural activity and lower extension of forested areas, possibly associated also to the effects of forest fires. The results suggest that conscious landscape management might contribute to determine a significant reduction in landslide susceptibility.
Major depressive disorder is prevalent in children and adolescents and is associated with a high degree of morbidity throughout life, with potentially devastating personal consequences and public ...health impact. The efficacy of ketamine (KET) as an antidepressant has been demonstrated in adolescent rodents; however, the neurobiological mechanisms underlying these effects are unknown. Recent evidence showed that KET reverses stress-induced (i.e., depressive-like) deficits within major mesocorticolimbic regions, such as the prefrontal cortex, nucleus accumbens (NAc), and hippocampus, in adult rodents. However, little is known about KET’s effect in the ventral tegmental area (VTA), which provides the majority of dopaminergic input to these brain regions.
We characterized behavioral, biochemical, and electrophysiological effects produced by KET treatment in C57BL/6J male mice during adolescence (n = 7–10 per condition) within the VTA and its major projection regions, namely, the NAc and prefrontal cortex. Subsequently, molecular targets within the VTA-NAc projection were identified for viral gene transfer manipulations to recapitulate the effects of stress or KET treatment.
Repeated KET treatment produced a robust proresilient response to chronic social defeat stress. This effect was largely driven by Akt signaling activity within the VTA and NAc, and it could be blocked or recapitulated through direct Akt-viral–mediated manipulation. Additionally, we found that the KET-induced resilient phenotype is dependent on VTA-NAc, but not VTA–prefrontal cortex, pathway activity.
These findings indicate that KET exposure during adolescence produces a proresilient phenotype mediated by changes in Akt intracellular signaling and altered neuronal activity within the VTA-NAc pathway.
A highly accurate analytical solution is derived to the electromagnetic problem of a short vertical wire antenna located on a stratified ground. The derivation consists of three steps. First, the ...integration path of the integrals describing the fields of the dipole is deformed and wrapped around the pole singularities and the two vertical branch cuts of the integrands located in the upper half of the complex plane. This allows to decompose the radiated field into its three contributions, namely the above-surface ground wave, the lateral wave, and the trapped surface waves. Next, the square root terms responsible for the branch cuts are extracted from the integrands of the branch-cut integrals. Finally, the extracted square roots are replaced with their rational representations according to Newton's square root algorithm, and residue theorem is applied to give explicit expressions, in series form, for the fields. The rigorous integration procedure and the convergence of square root algorithm ensure that the obtained formulas converge to the exact solution. Numerical simulations are performed to show the validity and robustness of the developed formulation, as well as its advantages in terms of time cost over standard numerical integration procedures.
Two decades ago, the observation of a rapid and sustained antidepressant response after ketamine administration provided an exciting new avenue in the search for more effective therapeutics for the ...treatment of clinical depression. Research elucidating the mechanism(s) underlying ketamine’s antidepressant properties has led to the development of several hypotheses, including that of disinhibition of excitatory glutamate neurons via blockade of N-methyl-d-aspartate (NMDA) receptors. Although the prominent understanding has been that ketamine’s mode of action is mediated solely via the NMDA receptor, this view has been challenged by reports implicating other glutamate receptors such as AMPA, and other neurotransmitter systems such as serotonin and opioids in the antidepressant response. The recent approval of esketamine (Spravato™) for the treatment of depression has sparked a resurgence of interest for a deeper understanding of the mechanism(s) underlying ketamine’s actions and safe therapeutic use. This review aims to present our current knowledge on both NMDA and non-NMDA mechanisms implicated in ketamine’s response, and addresses the controversy surrounding the antidepressant role and potency of its stereoisomers and metabolites. There is much that remains to be known about our understanding of ketamine’s antidepressant properties; and although the arrival of esketamine has been received with great enthusiasm, it is now more important than ever that its mechanisms of action be fully delineated, and both the short- and long-term neurobiological/functional consequences of its treatment be thoroughly characterized.
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