Arte e scienza in Charles Robert Darwin. Una nuova teoria estetica?

Il presente lavoro, fedelmente al titolo da cui si dipana, proverà a porre nel setaccio dello sguardo genealogico-analitico, due questioni strettamente intrecciate: 1) l’evoluzione, nelle viscere della biografia intellettuale darwiniana, del legame tra l’estetico e la costruzione della teoria scientifica; 2) la risoluzione della giovanile emergenza estetico-emozionale nella matura, collaudata, dinamica evolutivo-selettiva. La nostra narrazione procederà avvalendosi del prezioso viatico di una tripartizione euristico-finzionale, che richiama la legge dei tre stadi comtiana – nei confronti di cui Darwin, nei taccuini cosiddetti “metafisici”, manifestò apprezzamento ed entusiasmo. Ragion per cui paleseremo un “ever-increasing”, totalizzante, processo esistenzial-teoretico di scientifizzazione. Emergerà come la giovanile devozione di Darwin per l’humboldtiana “rara unione di poesia e scienza”, laddove, durante il quinquennale viaggio sul Beagle, l’olismo dello scienziato-esteta tedesco si accompagnava alla percezione di shelliani “dubbi terribili” evocati da una Natura, che sembrava essere più di un mero respiro della materia, lasciò viepiù il posto all’acribia “sperimentale” e macchinica del metodo scientifico. Dopo una fase “metafisica”, in cui l’emergenza estetica assunse una doppia connotazione, soggettiva, nel senso di momento creativo-immaginativo (“castles in the air”) propedeutico alla costruzione del cogente giudizio scientifico, e oggettiva, nel senso in cui l’attitudine estetica incarna viepiù le fattezze di un nodo estetico da sbrogliare naturalisticamente (“what is beauty?”), Darwin approdò ad una doppia legalistica risoluzione (selezione naturale/sessuale), all’interno di cui la giovanile misterica e palpitante Natura tropicale venne, per dirla con Lyotard, sacrificata sull’altare della legge (scientifica). Darwin, vent’anni dopo aver dato alle stampe quello che definì essere il suo “first literary child”, vale a dire il Journal of Researches (1839), il quale era ancora animato da strascichi humboldtiani, pubblicò l’Origin of Species (1859), nella cui intelaiatura il problema estetico divenne un’obiezione (teologica) alla teoria della selezione naturale da sciogliere utilitaristicamente. Obiezione che trovò il definitivo districamento in The Descent of Man, and Selection in Relation to Sex (1871), dove bellezza (“sense of beauty”) e scelta estetica (“taste”) furono assorbiti nelle fauci del meccanismo evolutivo di variazione, ereditarietà e selezione. Persino l’arte divenne un implicito corollario della selezione (sessuale). Malgrado quanto esposto, la progressiva narrazione comtiana dovrà fare i conti con una sorta di amara agnizione finale, in cui mostreremo - come attraverso la negativa di una positiva- i pericoli di un’ossessiva razionalizzazione della realtà naturale. Nell’Autobiography (1876-1882), Darwin, per l’appunto, affermò di esser diventato, invecchiando, sempre più una macchina estraente leggi, e con ciò perdendo il raffinato senso estetico giovanile, felicità, e creatività. Forse che un’eccessiva “positivizzazione” della realtà è deleteria, sia per l’uomo che per la scienza, nella misura in cui occulta, prima, deprime, poi, le radici emozionali della vita e del pensiero? D’altronde, stando al processo evolutivo stesso, le emozioni non rappresentarono l’imprescindibile brodo di coltura a partire da cui la ragione umana prese forma come, per dirla con Hume, un “meraviglioso e inintelligibile istinto”

Development of functional MRI protocols in the study of neurodegenerative diseases: MRI study in patients with REM sleep behavior disorder, idiopathic Parkinson's disease and multisystem atrophy

In the central nervous system, iron in several proteins is involved in many important processes: oxygen transportation, oxidative phosphorylation, mitochondrial respiration, myelin production, the synthesis and metabolism of neurotransmitters. Abnormal iron homoeostasis can induce cellular damage through hydroxyl radical production, which can cause the oxidation, modification of lipids, proteins, carbohydrates, and DNA, lead to neurotoxicity. Moreover increased levels of iron are harmful and iron accumulations are typical hallmarks of brain ageing and several neurodegenerative disorders particularly PD. Numerous studies on post mortem tissue report on an increased amount of total iron in the substantia nigra in patients with PD also supported by large body of in vivo findings from Magnetic Resonance Imaging (MRI) studies. The importance and approaches for in vivo brain iron assessment using multiparametric MRI is increased over last years. Quantitative MRI may provide useful biomarkers for brain integrity assessment in iron-related neurodegeneration. Particularly, a prominent change in iron- sensitive T2* MRI contrast within the sub areas of the SN overlapping with nigrosome 1 were shown to be a hallmark of Parkinson's Disease with high diagnostic accuracy. Moreover, differential diagnosis between Parkinson's Disease (PD) and atypical parkinsonian syndromes (APS) remains challenging, mainly in the early phases of the disease. Advanced brain MR imaging enables to detect the pathological changes of nigral and extranigral structures at the onset of clinical manifestations and during the course of the disease. The Nigrosome-1 (N1) is a substructure of the healthy Substantia Nigra pars compacta enriched by dopaminergic neurons; their loss in Parkinson’s disease and atypical parkinsonian syndromes is related to the iron accumulation. N1 changes are supportive MR biomarkers for diagnosis of these neurodegenerative disorders, but its detection is hard with conventional sequences, also using high field (3T) scanner. Quantitative susceptibility mapping (QSM), an iron-sensitive technique, enables the direct detection of Neurodegeneratio

Follow-Up Assessment of Intracranial Aneurysms Treated with Endovascular Coiling: Comparison of Compressed Sensing and Parallel Imaging Time-of-Flight Magnetic Resonance Angiography

The aim of our study was to compare compressed sensing (CS) time-of-flight (TOF) magnetic resonance angiography (MRA) with parallel imaging (PI) TOF MRA in the evaluation of patients with intracranial aneurysms treated with coil embolization or stent-assisted coiling. We enrolled 22 patients who underwent follow-up imaging after intracranial aneurysm coil embolization. All patients underwent both PI TOF and CS TOF MRA during the same examination. Image evaluation aimed to compare the performance of CS to PI TOF MRA in determining the degree of aneurysm occlusion, as well as the depiction of parent vessel and vessels adjacent to the aneurysm dome. The reference standard for the evaluation of aneurysm occlusion was PI TOF MRA. The inter-modality agreement between CS and PI TOF MRA in the evaluation of aneurysm occlusion was almost perfect (κ = 0.98, p < 0.001) and the overall inter-rater agreement was substantial (κ = 0.70, p < 0.001). The visualization of aneurysm parent vessel in CS TOF images compared with PI TOF images was evaluated to be better in 11.4%, equal in 86.4%, and worse in 2.3%. CS TOF MRA, with almost 70% scan time reduction with respect to PI TOF MRA, yields comparable results for assessing the occlusion status of coiled intracranial aneurysms. Short scan times increase patient comfort, reduce the risk of motion artifacts, and increase patient throughput, with a resulting reduction in costs. CS TOF MRA may therefore be a potential replacement for PI TOF MRA as a first-line follow-up examination in patients with intracranial aneurysms treated with coil embolization

Detrended fluctuation analysis of intertrade durations

The intraday pattern, long memory, and multifractal nature of the intertrade durations, which are defined as the waiting times between two consecutive transactions, are investigated based upon the limit order book data and order flows of 23 liquid Chinese stocks listed on the Shenzhen Stock Exchange in 2003. An inverse $U$-shaped intraday pattern in the intertrade durations with an abrupt drop in the first minute of the afternoon trading is observed. Based on the detrended fluctuation analysis, we find a crossover of power-law scaling behaviors for small box sizes (trade numbers in boxes) and large box sizes and strong evidence in favor of long memory in both regimes. In addition, the multifractal nature of intertrade durations in both regimes is confirmed by a multifractal detrended fluctuation analysis for individual stocks with a few exceptions in the small-duration regime. The intraday pattern has little influence on the long memory and multifractaility.Comment: 15 Elsart pages including 4 figures and 1 tabl

Status of the RFX experiment

The first results obtained in the RFX reversed field pinch experiment after the 1995 machine modifications are reported. The confinement, for fully stationary discharges at 0.6 MA, has now reached the expected values, even in the presence of MHD wall locked modes. Studies on locked mode effects have evidenced currents flowing from the plasma into the vessel in the region of locking. Measurements on plasma rotation and radial electric field have shown a perpendicular velocity shear at the edge similar to what is found in tokamaks and stellarators. New measurements on edge superthermal electrons and some evidence of their correlation with plasma core characteristics are included