Adenosine A3 receptors are widely distributed in the central nervous system but are expressed at ... more Adenosine A3 receptors are widely distributed in the central nervous system but are expressed at a low level and have lower affinity for adenosine in comparison to the A1 and A2A receptors. Nevertheless, they appear to tonically modulate motor activity as pointed out in A3 receptor-deleted mice. The role of A3 receptor in several pathophysiological conditions is often controversial. In conditions such as seizures or ischemia, when extracellular concentrations of adenosine increase, A3 receptors may contribute to neurotransmission and cell damage. A pro-convulsant effect of A3 receptor is feasible, especially in the immature brain, thus raising the possibility that A3 receptor might facilitate seizure-induced neuronal damage and activity-dependent plastic changes. Most data support a pro-nociceptive role of A3 receptor involving both central nervous system and pro-inflammatory effects at peripheral tissues. The outcome of A3 receptor stimulation on synaptic transmission during hypoxic/ischemic phenomena appears to depend on the duration and intensity of the ischemic episode. While A3 receptor may play a protective role in the first phase of ischemia by decreasing synaptic transmission, prolonged A3AR stimulation by high adenosine concentrations could be pivotal in transforming the A3AR-mediated effects from protective to injurious. Detrimental effects of A3AR activation may be due, at least in part, to increased excitoxicity. Glial A3AR stimulated by high adenosine levels caused by a prolonged central trauma may well be implicated in neuroinflammatory tissue responses.
In the context of the currently ongoing efforts to improve the accuracy and reliability of the me... more In the context of the currently ongoing efforts to improve the accuracy and reliability of the measurement of the Lense-Thirring effect in the gravitational field of the Earth it has recently been proposed to use the data from the existing spacecraft endowed with some active mechanisms of compensation of the non-gravitational accelerations like GRACE. In this paper we critically discuss this interesting possibility. Unfortunately, it turns out to be unpracticable because of the impact of the uncancelled even zonal harmonic coefficients of the multipolar expansion of the terrestrial gravitational potential and of some time-dependent tidal perturbations which would resemble as superimposed linear trends over the necessarily limited observational time span of the analysis.
In this work some aspects of the detection of certain general relativistic effects in the weak gr... more In this work some aspects of the detection of certain general relativistic effects in the weak gravitational field of the Earth via laser-ranged data to some existing or proposed geodetic satellites are examined. The focus is on the Lense-Thirring drag of the orbit of a test body, the gravitomagnetic clock effect and the gravitoelectric perigee shift. The impact of some sources of systematic errors is investigated. An experiment whose goal is the measurement of the PPN parameters beta and gamma in the terrestrial field with LAGEOS satellites at a level of 10^(-3)is presented. A modified version of the proposed LARES mission is examined.
In this paper we explore the possibility of suitably combining the nodes Ω of the existing geodet... more In this paper we explore the possibility of suitably combining the nodes Ω of the existing geodetic LAGEOS, LAGEOS II and Ajisai laser-ranged satellites and of the radar altimeter Jason–1 satellite in order to increase the accuracy in testing the general relativistic gravitomagnetic Lense–Thirring secular effect in the gravitational field of the Earth. The proposal of introducing Ajisai and Jason–1 in such a combination comes from the expected benefits which could be obtained in reducing the aliasing secular impact of the classical part of the terrestrial gravitational field. According to the recently released EIGEN-CG01C combined GRACE + CHAMP + terrestrial gravimetry/altimetry Earth gravity model, the impact of the static part of the mismodelled even zonal harmonics of geopotential, which represent the major source of systematic error, amounts to 1.6%, at 1−σ level. It is better than the error which could be obtained with a two-node LAGEOS-LAGEOS II only combination (6% at 1−σ). Moreover, the proposed combination would be insensitive also to the secular variations of the low-degree even zonal harmonics, contrary to the LAGEOS-LAGEOS II only combination. Such variations could be a serious limiting factor over observational time spans many years long. The price to be paid for this improvements of the systematic error of gravitational origin is represented by the non-conservative forces introduced along with the new orbital elements. However, they would induce periodic perturbations, contrary to the gravitational noise. A major concern would be the assessment of the impact of the non-conservative accelerations on the Jason–1 node. According to the present-day force models, the mismodelling in the non-conservative forces would, at worst, induce an aliasing periodic signal with an amplitude of 4% of the Lense-Thirring effect over a time span of 2 years. However, an observational time span of just some years could safely be adopted in order to fit and remove the residual long–period non-gravitational signals affecting Jason’s node, which, in the case of the direct solar radiation pressure, have a main periodicity of approximately 120 days. Of course, the possibility of getting time series of the Jason’s node some years long should be demonstrated in reality.
Adenosine A3 receptors are widely distributed in the central nervous system but are expressed at ... more Adenosine A3 receptors are widely distributed in the central nervous system but are expressed at a low level and have lower affinity for adenosine in comparison to the A1 and A2A receptors. Nevertheless, they appear to tonically modulate motor activity as pointed out in A3 receptor-deleted mice. The role of A3 receptor in several pathophysiological conditions is often controversial. In conditions such as seizures or ischemia, when extracellular concentrations of adenosine increase, A3 receptors may contribute to neurotransmission and cell damage. A pro-convulsant effect of A3 receptor is feasible, especially in the immature brain, thus raising the possibility that A3 receptor might facilitate seizure-induced neuronal damage and activity-dependent plastic changes. Most data support a pro-nociceptive role of A3 receptor involving both central nervous system and pro-inflammatory effects at peripheral tissues. The outcome of A3 receptor stimulation on synaptic transmission during hypoxic/ischemic phenomena appears to depend on the duration and intensity of the ischemic episode. While A3 receptor may play a protective role in the first phase of ischemia by decreasing synaptic transmission, prolonged A3AR stimulation by high adenosine concentrations could be pivotal in transforming the A3AR-mediated effects from protective to injurious. Detrimental effects of A3AR activation may be due, at least in part, to increased excitoxicity. Glial A3AR stimulated by high adenosine levels caused by a prolonged central trauma may well be implicated in neuroinflammatory tissue responses.
In the context of the currently ongoing efforts to improve the accuracy and reliability of the me... more In the context of the currently ongoing efforts to improve the accuracy and reliability of the measurement of the Lense-Thirring effect in the gravitational field of the Earth it has recently been proposed to use the data from the existing spacecraft endowed with some active mechanisms of compensation of the non-gravitational accelerations like GRACE. In this paper we critically discuss this interesting possibility. Unfortunately, it turns out to be unpracticable because of the impact of the uncancelled even zonal harmonic coefficients of the multipolar expansion of the terrestrial gravitational potential and of some time-dependent tidal perturbations which would resemble as superimposed linear trends over the necessarily limited observational time span of the analysis.
In this work some aspects of the detection of certain general relativistic effects in the weak gr... more In this work some aspects of the detection of certain general relativistic effects in the weak gravitational field of the Earth via laser-ranged data to some existing or proposed geodetic satellites are examined. The focus is on the Lense-Thirring drag of the orbit of a test body, the gravitomagnetic clock effect and the gravitoelectric perigee shift. The impact of some sources of systematic errors is investigated. An experiment whose goal is the measurement of the PPN parameters beta and gamma in the terrestrial field with LAGEOS satellites at a level of 10^(-3)is presented. A modified version of the proposed LARES mission is examined.
In this paper we explore the possibility of suitably combining the nodes Ω of the existing geodet... more In this paper we explore the possibility of suitably combining the nodes Ω of the existing geodetic LAGEOS, LAGEOS II and Ajisai laser-ranged satellites and of the radar altimeter Jason–1 satellite in order to increase the accuracy in testing the general relativistic gravitomagnetic Lense–Thirring secular effect in the gravitational field of the Earth. The proposal of introducing Ajisai and Jason–1 in such a combination comes from the expected benefits which could be obtained in reducing the aliasing secular impact of the classical part of the terrestrial gravitational field. According to the recently released EIGEN-CG01C combined GRACE + CHAMP + terrestrial gravimetry/altimetry Earth gravity model, the impact of the static part of the mismodelled even zonal harmonics of geopotential, which represent the major source of systematic error, amounts to 1.6%, at 1−σ level. It is better than the error which could be obtained with a two-node LAGEOS-LAGEOS II only combination (6% at 1−σ). Moreover, the proposed combination would be insensitive also to the secular variations of the low-degree even zonal harmonics, contrary to the LAGEOS-LAGEOS II only combination. Such variations could be a serious limiting factor over observational time spans many years long. The price to be paid for this improvements of the systematic error of gravitational origin is represented by the non-conservative forces introduced along with the new orbital elements. However, they would induce periodic perturbations, contrary to the gravitational noise. A major concern would be the assessment of the impact of the non-conservative accelerations on the Jason–1 node. According to the present-day force models, the mismodelling in the non-conservative forces would, at worst, induce an aliasing periodic signal with an amplitude of 4% of the Lense-Thirring effect over a time span of 2 years. However, an observational time span of just some years could safely be adopted in order to fit and remove the residual long–period non-gravitational signals affecting Jason’s node, which, in the case of the direct solar radiation pressure, have a main periodicity of approximately 120 days. Of course, the possibility of getting time series of the Jason’s node some years long should be demonstrated in reality.
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Papers by Stella Iorio