A CASE STUDY OF DIFFERENT LIMESTONES DURING QUICK LIME AND SLAKED-LIME PRODUCTION

We have examined 5 different limestones in order to study their behavior i) during calcination at different temperatures (900, 1050 and 1200°C for 30 min) and ii) after hydration of quick limes derived to slaked lime. Quick limes calcined at 900°C show the lower reactivity values. This could be related to the low calcination temperature or to the short calcination time of 30 min which was unable to produce enough lime. The samples calcined at temperatures of 1200°C are less reactive compared to the hydrated limes which were prepared by hydration of quick lime calcined at 1050°C, indicating by parameters such as the (CaO+MgO)Lime, the time required to become the temperature maximum and the reactivity rate. These, probably could be due to crystal growth at relative high temperatures

Static and non-static quantum effects in two-dimensional dilaton gravity

We study backreaction effects in two-dimensional dilaton gravity. The backreaction comes from an $R^2$ term which is a part of the one-loop effective action arising from massive scalar field quantization in a certain approximation. The peculiarity of this term is that it does not contribute to the Hawking radiation of the classical black hole solution of the field equations. In the static case we examine the horizon and the physical singularity of the new black hole solutions. Studying the possibility of time dependence we see the generation of a new singularity. The particular solution found still has the structure of a black hole, indicating that non-thermal effects cannot lead, at least in this approximation, to black hole evaporation.Comment: 10 pages, no figure

Mortality and Effect on Growth of Artemia franciscana Exposed to Two Common Organic Pollutants

Acute toxicity and inhibition on growth of Artemia franciscana nauplii (Instar I-II) after exposure to the reference toxicants bisphenol a (BPA) and sodium dodecyl sulfate (SDS) were studied. LC50 values were calculated and differences in body growth were recorded after 24, 48, and 72 h of exposure to the toxicants. The results indicated that BPA had lower toxicity than SDS. Development of the nauplii was clearly influenced by duration of exposure. Growth inhibition was detected for both toxicants. Abnormal growth of the central eye of several Artemia nauplii after 72 h of exposure to BPA was also detected. Our results indicate that growth inhibition could be used as a valid endpoint for toxicity studies

ATP signalling in epilepsy

This paper focuses on a role for ATP neurotransmission and gliotransmission in the pathophysiology of epileptic seizures. ATP along with gap junctions propagates the glial calcium wave, which is an extraneuronal signalling pathway in the central nervous system. Recently astrocyte intercellular calcium waves have been shown to underlie seizures, and conventional antiepileptic drugs have been shown to attenuate these calcium waves. Blocking ATP-mediated gliotransmission, therefore, represents a potential target for antiepileptic drugs. Furthermore, while knowledge of an antiepileptic role for adenosine is not new, a recent study showed that adenosine accumulates from the hydrolysis of accumulated ATP released by astrocytes and is believed to inhibit distant synapses by acting on adenosine receptors. Such a mechanism is consistent with a surround-inhibitory mechanism whose failure would predispose to seizures. Other potential roles for ATP signalling in the initiation and spread of epileptiform discharges may involve synaptic plasticity and coordination of synaptic networks. We conclude by making speculations about future developments

Effects of Cocaine-Kindling on the Expression of NMDA Receptors and Glutamate Levels in Mouse Brain

In the present study we examined the effects of cocaine seizure kindling on the expression of NMDA receptors and levels of extracellular glutamate in mouse brain. Quantitative autoradiography did not reveal any changes in binding of [3H] MK-801 to NMDA receptors in several brain regions. Likewise, in situ hybridization and Western blotting revealed no alteration in expression of the NMDA receptor subunits, NR1 and NR2B. Basal overflow of glutamate in the ventral hippocampus determined by microdialysis in freely moving animals also did not differ between cocaine-kindled and control groups. Perfusion with the selective excitatory amino acid transporter inhibitor, pyrrolidine-2,4-dicarboxylic acid (tPDC, 0.6 mM), increased glutamate overflow confirming transport inhibition. Importantly, KCl-evoked glutamate overflow under tPDC perfusion was significantly higher in cocaine-kindled mice than in control mice. These data suggest that enhancement of depolarization stimulated glutamate release may be one of the mechanisms underlying the development of increased seizure susceptibility after cocaine kindling

Neuroprotection by adenosine in the brain: From A1 receptor activation to A2A receptor blockade

Adenosine is a neuromodulator that operates via the most abundant inhibitory adenosine A1 receptors (A1Rs) and the less abundant, but widespread, facilitatory A2ARs. It is commonly assumed that A1Rs play a key role in neuroprotection since they decrease glutamate release and hyperpolarize neurons. In fact, A1R activation at the onset of neuronal injury attenuates brain damage, whereas its blockade exacerbates damage in adult animals. However, there is a down-regulation of central A1Rs in chronic noxious situations. In contrast, A2ARs are up-regulated in noxious brain conditions and their blockade confers robust brain neuroprotection in adult animals. The brain neuroprotective effect of A2AR antagonists is maintained in chronic noxious brain conditions without observable peripheral effects, thus justifying the interest of A2AR antagonists as novel protective agents in neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease, ischemic brain damage and epilepsy. The greater interest of A2AR blockade compared to A1R activation does not mean that A1R activation is irrelevant for a neuroprotective strategy. In fact, it is proposed that coupling A2AR antagonists with strategies aimed at bursting the levels of extracellular adenosine (by inhibiting adenosine kinase) to activate A1Rs might constitute the more robust brain neuroprotective strategy based on the adenosine neuromodulatory system. This strategy should be useful in adult animals and especially in the elderly (where brain pathologies are prevalent) but is not valid for fetus or newborns where the impact of adenosine receptors on brain damage is different

Gi/o-protein coupled receptors in the aging brain

Cells translate extracellular signals to regulate processes such as differentiation, metabolism and proliferation, via transmembranar receptors. G protein-coupled receptors (GPCRs) belong to the largest family of transmembrane receptors, with over 800 members in the human species. Given the variety of key physiological functions regulated by GPCRs, these are main targets of existing drugs. During normal aging, alterations in the expression and activity of GPCRs have been observed. The central nervous system (CNS) is particularly affected by these alterations, which results in decreased brain functions, impaired neuroregeneration, and increased vulnerability to neuropathologies, such as Alzheimer's and Parkinson diseases. GPCRs signal via heterotrimeric G proteins, such as Go, the most abundant heterotrimeric G protein in CNS. We here review age-induced effects of GPCR signaling via the Gi/o subfamily at the CNS. During the aging process, a reduction in protein density is observed for almost half of the Gi/o-coupled GPCRs, particularly in age-vulnerable regions such as the frontal cortex, hippocampus, substantia nigra and striatum. Gi/o levels also tend to decrease with aging, particularly in regions such as the frontal cortex. Alterations in the expression and activity of GPCRs and coupled G proteins result from altered proteostasis, peroxidation of membranar lipids and age-associated neuronal degeneration and death, and have impact on aging hallmarks and age-related neuropathologies. Further, due to oligomerization of GPCRs at the membrane and their cooperative signaling, down-regulation of a specific Gi/o-coupled GPCR may affect signaling and drug targeting of other types/subtypes of GPCRs with which it dimerizes. Gi/o-coupled GPCRs receptorsomes are thus the focus of more effective therapeutic drugs aiming to prevent or revert the decline in brain functions and increased risk of neuropathologies at advanced ages.This work was supported by Fundação para a Ciência e Tecnologia, Centro 2020 and Portugal 2020, the COMPETE program, QREN, and the European Union (FEDER program) via the GoBack project (PTDC/CVT-CVT/32261/2017), the pAGE program (Centro-01-0145-FEDER-000003), and Institute for Biomedicine iBiMED (UID/BIM/04501/2013; UID/BIM/04501/2019).publishe

Business tourism spending in eurozone countries: Detecting for convergence trends

The paper detects for convergence trends in terms of per capita business tourism spending among the Eurozone countries. The paper employs the methodological approach of gaps’ convergence clubs, and covers the period 2001-2018. The findings point to clear trends of convergence, indicating that business tourism seems to alleviate spatial externalities in the Eurozone economic space. This calls for a set of well-targeted and carefully-designed policy interventions focusing on promoting – and reaping the benefits of – business tourism. © Varna University of Management. All rights reserved

The Nexus of Tourism Spending with Economic Performance: A Panel Data Analysis for the Eurozone Area

The paper investigates the nexus of tourism spending (i.e. leisure and business tourism spending) with economic performance (i.e. GDP and employment) for the Eurozone countries, during the period 2000- 2018, employing sophisticated panel data analysis techniques. The issue is salient, given that within the Eurozone economic space the abolition of border impediments has released dynamics and brought into surface a new mix of opportunities, threats and challenges that has been changing the balance between centripetal and centrifugal forces. The findings of the paper identify the long-run equilibrium and confirm the bi-directional relationships among the variables considered, thus contributing to the discussion on the relationship between tourism and economic performance. © 2021. All rights reserve