196,210 research outputs found
Os Franciscos de Roma
No full textEnsaio sobre a presença de Francisco de Sá de Miranda, Francisco de Hollanda e Chico Buarque de Hollanda em Rom
Social structure
No full textSocial structure is one of the most controversial, yet at the same time crucial, concepts in sociological theory. It is a “powerful yet mystical metaphor”, according to Crothers [1996: vii], which touches upon some of the issues most important to social scientists, like the ambivalence between social action and systemic action. Nevertheless, many challenges present themselves when seeking to systematically examine the issue of social structure, particularly with respect to theoretical aspects.
First of all, in the absence of a common definition, it is necessary to establish the concept’s boundaries. Second, in every single theoretical perspective, the emphasis is placed on specific components of social structure, as well as on certain types of relationships that connect these components. Lastly, the choice of which components to consider and which relationships to identify within the social structure can be ascribed not only to the consistency with the theoretical reference paradigm but also to the historic reality and social environment that each academic is rooted in. Therefore, this paper will seek to create a synthetic outline and, by virtue of necessity, a partial review of the various attributes of social structure as well
Scali ferroviari, da infrastrutture di trasporto ad aree urbane
No full textC’è un grande tema, nella progettazione urbana degli anni duemila: è il recupero delle grandi aree produttive dismesse, e in particolare degli scali ferroviari non più utilizzati per il sistema del trasporto merci. Storicamente le ferrovie sono state concepite per svolgere il servizio viaggiatori e quello delle merci nell’ambito dello stesso impianto. Infatti l’impostazione ottocentesca delle stazioni, che si è mantenuta fino a pochi decenni fa, prevedeva un fabbricato viaggiatori in adiacenza ai binari di circolazione e sosta dei treni per il trasporto di persone e, a poca distanza, un fascio di binari adibiti alle operazioni sui convogli adibiti a quello che, nei manuali di procedura, veniva definito “trasporto delle cose”. Quest’ultimi convogli venivano scomposti e ricomposti, negli scali, a cura dei manovratori, e in fine rispediti per le varie destinazioni. La trasformazione organizzativa di fine Novecento ha portato alla concentrazione dei treni merci (pochi, purtroppo, dato il ben noto squilibrio a favore del trasporto stradale) in appositi centri intermodali e il progressivo abbandono degli scali, presenti pressoché in tutte le stazioni. Questi, ormai inutilizzati, hanno continuato a separare parti di città, generando trascuratezze e sempre più evidenti situazioni di degrado.
La consapevolezza di una possibile rigenerazione di quelle aree è stata acquisita, ma solo di recente e da una cerchia ristretta di amministratori. L’idea poi che quei “vuoti” possano costituire il fulcro per la progettazione di nuove aree urbane pulsanti di vita appartiene solo agli amministratori capaci di agire in una prospettiva a medio-lungo termine, di confrontarsi con una molteplicità di soggetti, di aprirsi alle idee innovative di architetti e urbanisti. Con un impegno che, al di là del consenso immediato, sia rivolto al futuro.
In questo numero dedicato al tema della trasformazione degli scali ferroviari vengono proposti dopo alcune riflessioni di carattere generale, tese a riaffermare il ruolo strategico che queste aree potrebbero svolgere nella riorganizzazione urbana complessiva, i casi di Milano (l’unica città dove gli amministratori hanno elaborato, d’intesa con le FS, progetti concreti per i sette scali merci dismessi, e ne hanno avviato l’attuazione), una panoramica che abbraccia il Veneto, con un primo piano su Verona, quindi sull’Emilia Romagna e le città di Genova e Napoli, ma anche alcuni casi esemplari stranieri, in Inghilterra, in Francia e Germania
Interaction of methamidophos with hen and human acetylcholinesterase and neuropathy target esterase
No full textMethamidophos causes acute cholinergic toxicity in several species, including man, and organophosphate-induced delayed polyneuropathy which has been reported in man but not in the hen. Acetylcholinesterase (AChE) and neuropathy target esterase (NTE) are thought to be the molecular targets of acute and delayed toxicity, respectively. The rate constants of inhibition (ka) and reactivation (k + 3) of human and hen brain AChE and NTE by methamidophos resolved optical isomers are here reported. NTE inhibition was progressive and irreversible. Human and hen NTE ka (M-1.m-1) for D-(+) methamidophos was 88 and 59, respectively, and for L-(-) methamidophos 3.2 and 3.0, respectively. AChE spontaneously reactivates after inhibition. D-(+) methamidophos 10(-3).ka (M-1.m-1) for human and hen AChE was 0.24 and 0.13; 10(3).k+3 (m-1) was 0.83 and 0.69, respectively. L-(-) Methamidophos 10(-3).ka (M-1.m-1) for human and hen AChE was 5.7 and 2.8, whereas 10(3).k+3 (m-1) was 6.50 and 1.52, respectively. L-(-)-Inhibited AChE reactivated to about 60% for human and 30% for hen enzymes, respectively. D-(+)-Inhibited AChE reactivated to about 10-20% for both species. Maximal reactivation occurred within 4-6 h when a plateau was reached. The larger and faster reactivation of human AChE inhibited in vitro by L-(-) methamidophos suggests that a corresponding effect might be possible in vivo and therefore explain, in part, the relatively higher susceptibility of man to delayed polyneuropathy induced by racemic methamidophos which occurs, however, with doses always causing severe cholinergic toxicity
AN O(MN) ALGORITHM FOR REGULAR SET-COVERING PROBLEMS
No full textAbstractA clutter L is a collection of m subsets of a ground set E(L) = {x1,…, xn} with the property that, for every pair Ai, Aj ϵ L, Ai is neither contained nor contains Aj, A transversal of L is a subset of E(L) intersecting every member of L.If we associate with each element xj ϵ E(L) a weight cj, the problem of finding a transversal having minimum weight is equivalent to the following set-covering problem min{cTx|MLx ⩾ 1m, xj ϵ {0, 1}, j = 1,…, n} where ML is the matrix whose rows are the incidence vectors of the subsets Ai ϵ L and 1m denotes the vector with m ones.A set-covering problem is regular if there exists an ordering of the variables σ = (x1,…, xn) such that, for every feasible solution x with xi = 1, xj = 0, j < i, the vector x + ej − ei is also a feasible solution, where ei is the ith unit vector. The matrix M of a regular set-covering problem is said to be regular.A regular clutter is any clutter whose incidence matrix is regular. In this paper we describe some properties of regular clutters and propose an algorithm which, in O(mn) steps, generates all the minimal transversals of a regular clutter L and produces the transversal having minimum weight
The phosphorothioic acid O-(2-chloro-2,3,3-trifluorocyclobutyl) O-ethyl S-propyl ester exacerbates organophosphate polyneuropathy without inhibition of neuropathy target esterase
No full textOrganophosphate-induced delayed polyneuropathy (OPIDP) is thought to be initiated by a variety of neuropathy target esterase (NTE) inhibitors. However, certain inhibitors such as phenylmethanesulfonyl fluoride, phenyl N-methyl N-benzyl carbamate, and phenyl di-n-pentyl phosphinate protect from OPIDP when given to hens before organophosphorus esters. They protect from neuropathy by preventing the binding of neuropathic inhibitors to NTE catalytic site. In contrast, when such NTE inhibitors are given afterward, the resulting clinical effect is more severe. This phenomenon was called promotion of OPIDP. Promotion has been tentatively explained by the interaction of promoters with a target other than the catalytic center of NTE. However, the doses of promoters which cause the effect have, so far, been found to always be inhibitory of NTE. We report that the phosphorothioic acid O-(2-chloro-2,3,3-trifluorocyclobutyl) O-ethyl S propyl ester (KBR-2822) given to hens at doses which did not inhibit NTE (2.5 mg/kg p.o.) promoted the neuropathies initiated by either dibutyl-2,2-dichlorovinyl phosphate (DBDCVP, 0.4 mg/kg s.c., 24 hr earlier) or diisopropyl phosphorofluoridate (DFP, 0.3 mg/kg sc or 0.5 mg/kg s.c., 24 hr earlier). When given alone, DBDCVP and DFP (0.5 mg/kg) caused mild OPIDP, whereas the lower dose of DFP did not cause clinical effects. Dose-response relationships with KBR-2822 indicated that clinical effects of the combined treatments are unlikely to be additive because the compound did not cause OPIDP up to the maximum tolerated dose (10 mg/kg p.o.). Promotion also occurred when KBR-2822 (2.5 mg/kg p.o.) was given before either DBDCVP (0.4 mg/kg s.c.) or DFP (0.3 mg/kg s.c.). NTE inhibitions in the nervous tissues caused by DBDCVP or DFP were not affected by pretreatment with KBR-2822, suggesting that the delivery of neuropathic. NTE inhibitors was not modified. We conclude that KBR-2822 promotes OPIDP initiated by either DBDCVP or DFP by affecting a target other than NTE catalytic site
The phosphorothioic acid O-(2-choro-2,3,3-trifluorocyclobutyl) O-ethyl S-propyl ester exacerbates organophosphate polyneuropathy without inhibition of neuropathy target esterase
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