73 resultados para Jacobson Radical
Resumo:
Radical anions of 1-bromo-4-nitrobenzene (p-BrC6H4NO2) are shown to be reactive in the room temperature ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, ([C(4)mPyrr][NTf2]), by means of voltammetric measurements. In particular, they are shown to react via a DISP type mechanism such that the electrolysis of p-BrC6H4NO2 occurs consuming between one and two electrons per reactant molecule, leading to the formation of the nitrobenzene radical anion and bromide ions. This behaviour is a stark contrast to that in conventional non-aqueous solvents such as acetonitrile, dimethyl sulfoxide or N,N-dimethylformamide, which suggests that the ionic solvent promotes the reactivity of the radical anion, probably via stabilisation of the charged products.
Resumo:
A direct connection between comics and contemporary critical theory is to be found in the activity of the collective of artists who created "Cannibale" and "Frigidaire", the two most innovative Italian comics magazines of the late 1970s and early 1980s. The work of Andrea Pazienza, Filippo Scòzzari, Stefano Tamburini, Tanino Liberatore and Massimo Mattioli should be regarded as an expression of the radical movements from which Marxist Autonomist thinkers such as Antonio Negri, Franco ‘Bifo’ Berardi and Paolo Virno also emerged in the same period. As a consequence, the writings of the latter can be used to analyse the narrative and visual style, the recurring themes, and the editorial characteristics of the comics of the former. Moreover, an interesting parallel can also be drawn between the work of the most influential of these artists, Andrea Pazienza, and the thought of another prominent Italian philosopher, Giorgio Agamben, whose earliest books were published at that time too. The aim of this article is to show that the ideas of a number of the thinkers who have recently become internationally known as representatives of radical Italian theory, are useful to understand the work of this group of comics authors.
Resumo:
The metabolic vasodilator mediating postexercise hypotension (PEH) is poorly understood. Recent evidence suggests an exercise-induced reliance on pro-oxidant-stimulated vasodilation in normotensive young human subjects, but the role in the prehypertensive state is not known.
Resumo:
AIMS: To investigate the potential dosimetric and clinical benefits predicted by using four-dimensional computed tomography (4DCT) compared with 3DCT in the planning of radical radiotherapy for non-small cell lung cancer.
MATERIALS AND METHODS:
Twenty patients were planned using free breathing 4DCT then retrospectively delineated on three-dimensional helical scan sets (3DCT). Beam arrangement and total dose (55 Gy in 20 fractions) were matched for 3D and 4D plans. Plans were compared for differences in planning target volume (PTV) geometrics and normal tissue complication probability (NTCP) for organs at risk using dose volume histograms. Tumour control probability and NTCP were modelled using the Lyman-Kutcher-Burman (LKB) model. This was compared with a predictive clinical algorithm (Maastro), which is based on patient characteristics, including: age, performance status, smoking history, lung function, tumour staging and concomitant chemotherapy, to predict survival and toxicity outcomes. Potential therapeutic gains were investigated by applying isotoxic dose escalation to both plans using constraints for mean lung dose (18 Gy), oesophageal maximum (70 Gy) and spinal cord maximum (48 Gy).
RESULTS:
4DCT based plans had lower PTV volumes, a lower dose to organs at risk and lower predicted NTCP rates on LKB modelling (P < 0.006). The clinical algorithm showed no difference for predicted 2-year survival and dyspnoea rates between the groups, but did predict for lower oesophageal toxicity with 4DCT plans (P = 0.001). There was no correlation between LKB modelling and the clinical algorithm for lung toxicity or survival. Dose escalation was possible in 15/20 cases, with a mean increase in dose by a factor of 1.19 (10.45 Gy) using 4DCT compared with 3DCT plans.
CONCLUSIONS:
4DCT can theoretically improve therapeutic ratio and dose escalation based on dosimetric parameters and mathematical modelling. However, when individual characteristics are incorporated, this gain may be less evident in terms of survival and dyspnoea rates. 4DCT allows potential for isotoxic dose escalation, which may lead to improved local control and better overall survival.
Resumo:
Intrafraction tumour motion is an issue that is of increased interest in the era of image-guided radiotherapy. It is particularly relevant for non-small cell lung cancer, for which a number of recent developments are in use to aid with motion management in the delivery of radical radiotherapy. The ability to deliver hypofractionated ablative doses, such as in stereotactic radiotherapy, has been aided by improvements in the ability to analyse tumour motion and amend treatment delivery. In addition, accounting for tumour motion can enable dose escalation to occur by reducing the normal tissue being irradiated by virtue of a reduction in target volumes. Motion management for lung tumours incorporates five key components: imaging, breath-hold techniques, abdominal compression, respiratory tracking and respiratory gating. These will be described, together with the relevant benefits and associated complexities. Many studies have described improved dosimetric coverage and reduced normal tissue complication probability rates when using motion management techniques. Despite the widespread uptake of many of these techniques, there is a paucity of literature reporting improved outcome in overall survival and local control for patients whenever motion management techniques are used. This overview will review the extent of lung tumour motion, ways in which motion is detected and summarise the key methods used in motion management.
Resumo:
Glycolaldehyde, the simplest monosaccharide sugar, has recently been detected in low- and high-mass star-forming cores. Following our previous investigation into glycolaldehyde formation, we now consider a further mechanism for the formation of glycolaldehyde that involves the dimerization of the formyl radical, HCO. Quantum mechanical investigation of the HCO dimerization process upon an ice surface is predicted to be barrierless and therefore fast. In an astrophysical context, we show that this mechanism can be very efficient in star-forming cores. It is limited by the availability of the formyl radical, but models suggest that only very small amounts of CO are required to be converted to HCO to meet the observational constraints.
Resumo:
A new pathway to (+)-inthomycin C is reported that exploits an O-directed free radical hydrostannation reaction on (−)-12 and a Stille cross-coupling as key steps. Significantly, the latter process was effected on 19 where a gauche-pentane repulsive interaction could interfere. Our stereochemical studies on the alkynol (−)-12 and the enyne (+)-7 confirm that Ryu and Hatakeyama’s (3S)-stereochemical revision of (+)-inthomycin C is invalid and that Zeeck and Taylor’s original (3R)-stereostructure for (+)-inthomycin C is correct.
Resumo:
Abstract Image
Herein a new double O-directed free radical hydrostannation reaction is reported on the structurally complex dialkyldiyne 11. Through our use of a conformation-restraining acetal to help prevent stereocenter-compromising 1,5-H-atom abstraction reactions by vinyl radical intermediates, the two vinylstannanes of 10 were concurrently constructed with high stereocontrol using Ph3SnH/Et3B/O2. Distannane 10 was thereafter elaborated into the bis-vinyl iodide 9 via O-silylation and double I–Sn exchange; double Stille coupling of 9, O-desilylation, and oxidation thereafter furnished 8.
Resumo:
The absolute yield of hydroxyl radicals per unit of deposited X-ray energy is determined for the first time for irradiated aqueous solutions containing metal nanoparticles based on a “reference” protocol. Measurements are made as a function of dose rate and nanoparticle concentration. Possible mechanisms for hydroxyl radical production are considered in turn: energy deposition in the nanoparticles followed by its transport into the surrounding environment is unable to account for observed yield whereas energy deposition in the water followed by a catalytic-like reaction at the water-nanoparticle interface can account for the total yield and its dependence on dose rate and nanoparticle concentration. This finding is important because current models used to account for nanoparticle enhancement to radiobiological damage only consider the primary interaction with the nanoparticle, not with the surrounding media. Nothing about the new mechanism appears to be specific to gold, the main requirements being the formation of a structured water layer in the vicinity of the nanoparticle possibly through the interaction of its charge and the water dipoles. The massive hydroxyl radical production is relevant to a number of application fields, particularly nanomedicine since the hydroxyl radical is responsible for the majority of radiation-induced DNA damage.
Resumo:
Highly reactive radicals play an important role in high-temperature gasification processes. However, the effect of radicals on gasification has not been systematically investigated. In the present study, the formation of carbon-radical precursors using atomic radicals such as OH, O, and H and molecules such as H2 and O2 was characterized, and the effect of the precursors on the adsorption step of steam char gasification was studied using quantum chemistry methods. The results revealed that the radicals can be chemisorbed exothermically on char active sites, and the following order of reactivity was observed: O > H2 > H > OH > O 2. Moreover, hydrogen bonds are formed between steam molecules and carbon-radical complexes. Steam molecule adsorption onto carbon-O and carbon-OH complexes is easier than adsorption onto clean carbon surfaces. Alternatively, adsorption on carbon-O2, carbon-H2, and carbon-H complexes is at the same level with that of clean carbon surfaces; thus, OH and O radicals accelerate the physical adsorption of steam onto the char surface, H radical and O2 and H2 molecules do not have a significant effect on adsorption. © 2010 American Chemical Society.
Resumo:
How did the counter-cultural aims of Radical Psychiatry coincide with those of documentary filmmaking in the 1960s? Where the forms and structures of new approaches to the documentary necessarily complicit in promoting the clinical and anti-clinical practices, and wider political agenda, of Radical Psychiatry? How did the documentary deal with the ethical, aesthetic, and audience-related issues associated with filming personalities and environments associated with Radical Psychiatry? How did Radical Psychiatry and the documentary shape postwar discourses on trauma, especially within conflict and post-conflict (PTSD) contexts? What is the legacy of Radical Pschiatry today, and how has it been explored by contemporary documentray film?
This article addresses these question by examining a range of documentaries dealing with the radical and 'anti-psychiatric' ideas and methods of figures such as R.D.Laing, David Cooper, Jan Bastiaans, Timothy Leary, and Franco Basaglia. Films analysed include Peter Robinson's Asylum (1972) and Psychiatry and Violence (1973); Ah, Sunflower (Klinkert and Sinclair, 1967); Anatomy of Violence (Davis, 1967); Turn On, Tune In, Drop Out (Robin Clarke, 1967), W. R. - Mysteries of the Organism (Makavejev, 1971); Raymond Depardon's San Clemente (1980) and Urgences (1988); and Louis van Gasteren's trilogy Now Do You Get it Why I am Crying (1969), The Price of Survival (2003), and There is No Plane to Zagreb (2012).
The article concludes with a discussion of Nicolas Philibert's Every Little Thing (1997) within the context of the French documentary tradition and the film's more immediate subject - the famous clinic at La Borde established by Jean Oury, and associated with the methods and theories of figures such as Jacques
Lacan, Francesc Tosquelles, Franz Fanon, and Félix Guattari.
Resumo:
Photoexcited electrochemically generated quinone radical anions reduced 1,2-dibromobenzene to bromobenzene, 1,4-dibromobenzene to bromobenzene and 4-chlorobenzonitrile to benzonitrile. In the presence of anthracene, 2-bromophenyl-, 4-bromophenyl- and 4-cyanophenyl-anthracenes were formed. With acetaldehyde, acetone, acetophenone, benzaldehyde and benzophenone, the major products were the corresponding pinacols, with small amounts of the two-electron secondary alcohols. In acetonitrile as solvent, cinnamonitriles, hydrocinnamonitriles and phenylglutaronitriles were formed in addition to the alcohols. Glyoxylic acid was reduced to tartaric, glycolic and malic acids. The reduction of CO2 was unsuccessful.