A high-resolution neutron spectroscopic camera for the SPARC tokamak based on the Jet European Torus deuterium-tritium experience

Dedicated nuclear diagnostics have been designed, developed, and built within EUROFUSION enhancement programs in the last ten years for installation at the Joint European Torus and capable of operation in high power Deuterium-Tritium (DT) plasmas. The recent DT Experiment campaign, called DTE2, has been successfully carried out in the second half of 2021 and provides a unique opportunity to evaluate the performance of the new nuclear diagnostics and for an understanding of their behavior in the record high 14 MeV neutron yields (up to 4.7 × 10¹⁸ n/s) and total number of neutrons (up to 2 × 10¹⁹ n) achieved on a tokamak. In this work, we will focus on the 14 MeV high resolution neutron spectrometers based on artificial diamonds which, for the first time, have extensively been used to measure 14 MeV DT neutron spectra with unprecedented energy resolution (Full Width at Half Maximum of ≈1% at 14 MeV). The work will describe their long-term stability and operation over the DTE2 campaign as well as their performance as neutron spectrometers in terms of achieved energy resolution and high rate capability. This important experience will be used to outline the concept of a spectroscopic neutron camera for the SPARC tokamak. The proposed neutron camera will be the first one to feature the dual capability to measure (i) the 2.5 and 14 MeV neutron emissivity profile via the conventional neutron detectors based on liquid or plastics scintillators and (ii) the 14 MeV neutron spectral emission via the use of high-resolution diamond-based spectrometers. The new opportunities opened by the spectroscopic neutron camera to measure plasma parameters will be discussed.

Tumor necrosis factor-α impairs oligodendroglial differentiation through a mitochondria-dependent process

Mitochondrial defects, affecting parameters such as mitochondrial number and shape, levels of respiratory chain complex components and markers of oxidative stress, have been associated with the appearance and progression of multiple sclerosis. Nevertheless, mitochondrial physiology has never been monitored during oligodendrocyte progenitor cell (OPC) differentiation, especially in OPCs challenged with proinflammatory cytokines. Here, we show that tumor necrosis factor alpha (TNF-α) inhibits OPC differentiation, accompanied by altered mitochondrial calcium uptake, mitochondrial membrane potential, and respiratory complex I activity as well as increased reactive oxygen species production. Treatment with a mitochondrial uncoupler (FCCP) to mimic mitochondrial impairment also causes cells to accumulate at the progenitor stage. Interestingly, AMP-activated protein kinase (AMPK) levels increase during TNF-α exposure and inhibit OPC differentiation. Overall, our data indicate that TNF-α induces metabolic changes, driven by mitochondrial impairment and AMPK activation, leading to the inhibition of OPC differentiation.

[Postischemic dysfunction and persistent ischemia in the early postinfarction period. Evaluation by echo-dobutamine-atropine test]

AIM

To study post-ischemic dysfunction and persistent ischemia in early post-infarction, by means of Echo-dobutamine-Atropine stress test (ECHO-DOB). Methods. We studied 138 patients (pts) aged < or = 75 yrs (mean 59.2 +/- 9.8) at their first uncomplicated myocardial infarction (AMI), treated with systemic thrombolysis. All pts underwent the test within 2 weeks since the onset of the attack and they were reevaluated in follow-up 3 months later. Under Echo and ECG monitoring, ECHO-DOB was performed according to EDICS protocol. Low doses was infused (5-10 mcg/Kg/min every 3') to assess the viability and high doses (20 > or = 40 mg/Kg/min + Atropine) to assess a possible persistent ischemia. The Wall Motion Score Index (WMSI) was used for the semiquantitative analysis of kinesis in a model of left ventricle divided into 16 segments. coronary angiography was performed within 30 days from the AMI, in 82.3% of pts. Results. Low dose of Dobutamine (DOB) induced in 92/136 (67.6%) pts an improvement in the contractile dysfunction in the region of necrosis; in 31.5% (29/92) it remained until the end of the test, suggesting the presence of viable myocardium, In absence of myocardium "at risk". High doses DOB induced worsening of contractile dysfunction in 64 pts (47%); in 40 (62.5%) viability had been previously detected (viable but ischemic myocardium); In 30 (75%) it was homozone or adjacent (viable but ischemic myocardium in the region of the coronary artery or in the tributary vessels correlated to the necrosis). In 24/64 (37.5%) pts the absence of modification of WMSI (no improvement and no worsening), suggested the presence of necrotic tissue in the tributary region of the vessel of necrosis. The significant improvement in kinesis revealed in 92 pts, by the follow-up control was confirmed in 64 (p < 0.001) (69.5%). Forty-four pts without hyperkinesia showed no significant improvement compared with the base line (stunned or hibernating myocardium). The sensitivity of low doses for viable myocardium (gold standard follow-up) was 69%; specificity was 77%. The sensitivity of high doses for ischemia (gold standard coronary arteriography) was 78%; specificity was 100%. No major side effects during the Dobutamine Atropine test were observed.

CONCLUSIONS

The ECHO-DOB test in the post-infarction period allow the assessment of the functional significance of what is the objectified by coronary angiography and identifies pts at risk of more serious events. An integration of the test with the angiographic data can direct towards more suitable therapeutical or surgical choices.

[Identification of ischemic and/or viable myocardium in early post-infarction period using echocardiographic imaging technique. Comparison of 2 tests: echo-dipyridamole and echo-dobutamine]

AIM OF THE STUDY

To compare two stress tests: Dipyridamole-echocardiography (ECHO-DIP) and Dobutamine-echocardiography (ECHO-DOB) with angiographic data (still "gold standard") in early postinfarction period in order to identify ischemic and/or viable myocardium (considering the echocardiographic follow-up as "gold standard").

METHODS

40 consecutive patients (pts), mean age 56, at their first uncomplicated acute myocardial infarction (AMI) treated with thrombolytic agents were studied. All underwent coronary angiography.

RESULTS

The ECHO-DIP test resulted positive in 17 pts for transient regional asynergy (homozone 13/17; heterozonal positivity 4/17). The mean basal Wall Motion Score Index (WMSI) was 0.46 +/- 0.30 and at asynergy was 0.58 +/- 0.33 (p < 0.001). The ECHO-DOB test resulted positive in 20 pts; mean basal WMSI was 0.42 +/- 0.31 and at asynergy 0.55 +/- 0.35 (p < 0.001). Both tests were positive in 14 pts; the site of regional asynergy was the same in each test. During ECHO-DOB hypercinesia appeared in 27/39 pts (WMSI form basal 0.42 +/- 0.31 to 0.22 +/- 0.21 p < 0.001). Recovery of contractile function seems to identify viable myocardium: viable tissue shows early functional recovery during ECHO-DOB infusion. In 14 pts it remained until the end of the test, and in 12 it was transient, denoting the presence of myocardium "at risk". Remote (3- or 6-month) clinical and echocardiographic follow-up were carried out in all pts (25 undergoing medical therapy and 15 after PTCA or coronary bypass). In 26 pts with hyperkinesia at ECHO-DOB, basal echocardiogram revealed improvement of WMSI from 0.42 +/- 0.31 to 0.32 +/- 0.29 (p < 0.001).

CONCLUSIONS

"Passive" ECHO-stress tests in the early postinfarction period are easy to perform and free of major risks, they allow pts at risk due to residual ischemia to be revealed with a high degree of specificity and sensitivity. The improvement of kinesis during inotropic stimulus of Dobutamine suggests stunned or hibernating myocardium.

[Intermittent atrio-ventricular block induced by exertion. Description of 3 cases]

Three patients with 1:1 atrio-ventricular conduction at rest developed fixed 2nd or 3rd degree atrio-ventricular block during exercise testing. In all patients electrophysiologic study documented block distal to the atrioventricular node. The exercise induced block probably occurred because of increased atrial rate and abnormal refractoriness of the His-Purkinje conduction system. These findings suggest that high degree atrioventricular block appearing during exercise reflects conduction disease of the His-Purkinje system rather than of the atrio-ventricular node, even in absence of bundle branch block. These patients should be considered for permanent cardiac pacing.

[Recurrent bradysystolic arrhythmia caused by closed thoracic trauma]

A case of slight thoracic trauma, part of more serious traumatism of the pelvis which developed a rare form of recurrent bradysystolia due to progressive slowdown of the sinus-atrial node, is reported. Emergency treatment with temporary i.v. electric stimulation allowed the patient to surmount the crisis and complete cure has now been evident for 8 months.