1,297 research outputs found
Interactions of Nitric Oxide with Lipid Peroxidation Products under Aerobic Conditions: Inhibitory Effects on the Formation of Malondialdehyde and Related Thiobarbituric Acid-Reactive Substances.
No full textUnder aerobic conditions, exposure of peroxidized lipids to nitric oxide (NO) was found to result in a rapid decrease in the levels of thiobarbituric acid-reactive substances (TEARS), Addition of 10-100 mu M NO to rat brain homogenates preincubated for 2 h at 37 degrees C caused up to a 20% decrease in the levels of TEARS compared to controls. A similar inhibitory effect was observed on TEARS produced by Fe2+-induced decomposition of 15-hydroperoxyeicosatetraenoic acid (15-HPETE), due apparently to NO-induced decomposition of the hydroperoxide (ferrous oxidation/xylenol orange assay). Prostaglandin G(2) (PGG(2), 35 mu M), as a model bicyclic endoperoxide, and malondialdehyde (MDA, 20 mu M), the main component of TEARS, proved also susceptible to degradation by NO or NO donors (diethylamine NONOate, DEA/NO) at concentrations of 100 mu M or higher in 0.05 M phosphate buffer, pH 7.4, and at 37 degrees C, as indicated by the reduced response to the TEA assay. No significant effect on TEARS determination was caused by nitrite ions. These and other data indicate that NO can inhibit TEARS formation by decomposing primary lipid peroxidation products, chiefly 15-HPETE and related hydroperoxides, and, to a lesser extent, later stage TEARS precursors, including bicyclic endoperoxides and MDA, via nitrosation and other oxidative routes, without however affecting chromogenic reactions during the assay
Regulatory and Environmental Effects on Public Transit Efficiency. A Mixed Dea-Sfa Approach
No full textThis paper assesses the impact of regulatory and environmental factors and statistical noise on the efficiency of public transit systems within a DEA-based framework. Using a panel of Italian companies, we implement a DEA-SFA mixed approach based on [H.O. Fried et al. (2002) Journal of Productivity Analysis, 17(1–2),
157–174] to decomposeDEAinefficiencymeasures into three components: exogenous effects, managerial inefficiency and stochastic events. Besides providing evidence on the determinants of input-specific efficiency differentials across companies, the results point out that managerial skills play a minor role, and emphasize the relevance of regulatory policies aimed at replacing cost-plus subsidization with high-powered
incentive contracts as well as improving environmental conditions of public transit networks
In vivo interaction of lead with aminolevulinic acid dehydratase and induction of a thermolabile factor: an experimental model.
No full textAminolevulinic acid dehydratase (ALA-D) activity of male albino Wistar rats was used as an experimental model for a study on the interaction of lead with biological systems. Lead at 1 mg/kg was administered i.p. and the rats were killed immediately, and at 30 min, 1, 2, 3, and 4 h after treatment. It was shown that lead (Pb) interacted directly with the enzyme molecule immediately after treatment, first on the active site of zinc (Zn) and then on the thiolic groups. Induction of the so-called thermolabile factor (TF) seemed to occur later, i.e., it may only be shown from the 2nd-3rd h after treatment. The long-term persistence of lead-induced TF in the acute phase of intoxication may be the key to the interpretation of some chronic toxic effects
Modeling of Electromagnetic Sources by Means of a Genetic Algorithm
No full textPresented in: Workshop W1 - Field-Based Synthesis and Computer Aided Design of Electromagnetic Structure
Validazione sul campo dei campionatori passivi per la determinazione ambientale della formaldeide.
No full textno abstract availabl
Quantificazione del rischio da 1,2-dicloropropano in alcune lavorazioni industriali.
No full textno abstract availabl
Regolamentazione incentivante nel trasposto pubblico locale fra teoria e pratica: quale lezione dallo studio delle frontiere di efficienza?
No full textIl presente lavoro si propone di valutare, su un campione di 42 operatori pubblici italiani di Trasporto Pubblico Locale (TPL) osservati tra 1993 e 1999, l’impatto delle condizioni strutturali del network e di regolamentazione sui divari di efficienza, attraverso la combinazione delle due metodologie DEA (Data Envelopment Analysis) e SFA (Stochastic Frontier Approach). In un primo step sono stati calcolati score DEA di efficienza e valori di slack per ogni input. In un secondo step, questi ultimi sono stati regrediti, attraverso un approccio panel SFA (Battese e Coelli, 1992), su un insieme di variabili esogene indicative sia delle caratteristiche del network sia del contesto regolatorio. Il focus, in particolare, Ã ̈ posto sull’efficacia del cambio di regime di regolamentazione da contratti di affidamento di tipo cost-plus a modelli piÃ1 incentivanti di tipo fixed-price. I risultati evidenziano una prevalente portata esplicativa degli effetti esogeni “strutturali” e, secondariamente, di noise nella spiegazione dei divari di efficienza, riservando un
ruolo minore al fattore di efficienza manageriale pura, specialmente con riferimento al lavoro diretto (impiegato nell’attività di conduzione dei veicoli) e ai costi operativi per materiali e servizi. Come conclusione di policy, ed in accordo con le previsioni della New Theory of Regulation (NTR), si rileva come il sistema italiano di regolamentazione, attraverso la
formulazione di appropriati cap, si sia incentrato proprio su quei fattori maggiormente sensibili all’intensificazione dell’effort, e per i quali si rendeva, pertanto, necessaria, una piÃ1 decisa azione
di razionalizzazione
Regolamentazione incentivante nel trasporto pubblico locale fra teoria e pratica: quale lezione dallo studio di frontiere di efficienza?
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