Search results for "Zen"

Structural Signatures of Type IV Isotherm Steps:  Sorption of Trichloroethene, Tetrachloroethene, and Benzene in Silicalite-I

2002

We have investigated by in situ neutron diffraction the structural properties of C2HCl3, C2Cl4, and C6D6 sorbed phases in silicalite-1. Our motivation is to correlate the structure of these three confined species to the fact that their adsorption isotherms are characterized by no step, one step, and two steps, respectively. From our detailed neutron diffraction investigation, we deduce that the adsorption isotherm steps are not signatures of phase transitions but are correlated to the different adsorption stages observed during the silicalite-1 loading. For C6D6, such a loading is a three stage process (the C6D6 molecules fill successively, the intersections, then the straight channels and …

Conflictos ambientales y ciudadanía ecológica: el caso de Gualeguaychú y los pulp mills

2019

This article deals with interactions between citizenship and political ecology by examining the ‘pulp mills conflict’ in Gualeguaychú, Argentina. The conflict burst in 2003 when the Uruguayan authorities announced the construction of a cellulose plant on the shore of the Uruguay River. The citizens of Gualeguaychú, a city right across the border, initiated a movement of protest that soon transcended the local dimension. I argue that this protest was a battle over sovereignty and an environmental conflict between different conceptions of development and diverse views of the use of a common resource, the river. The notion of ecological citizenship formed in this process is assessed by examini…

From Carneades to Cicero

2015

This chapter is about how Stoic epistemology developed in the two centuries after Chrysippus’ death. I first show that, as a result of Carneades’ critique in the mid-second century, there was a shift of emphasis in the epistemological debate between the Stoa and the Academy. From then on the task was not to explain what causal features a cognitive thought has, but to describe what phenomenological features it has. I show that the later Stoics responded to this challenge in two different ways. Some changed Chrysippus’ theory quite radically. They held that a cognitive thought is characterized by giving rise to a sense of conviction, denied that preconceptions count as cognitive thoughts, and…

Tragedia griega: una metáfora de debate público y participación democrática

2019

Athenian citizens deliberate in the assembly, but the theatre also becomes a place for public debate. In addition to being a consequence of economic or cultural aspects, democracy is a consequence of the development of a democratic imaginary. Located in that imaginary, Greek tragedies, regarded as «democratic myths», work to reaffirm Athenian democracy. Far from being dogmatic, the tragic myth explores the contradictions of social and personal life and implicitly or explicitly seeks their correction. This dramatic genre encourages participation from the spectator (citizen) that greatly exceeds the schematic reduction in Aristotelian theory of catharsis. Greek tragedy proposes the existence …

ASPECTS OF CITIZENSHIP - (A.) Duplouy, (R.) Brock (edd.) Defining Citizenship in Archaic Greece. Pp. xiv + 370. Oxford: Oxford University Press, 2018…

2019

Phosphorylated micro- vs. nano-cellulose: a comparative study on their surface functionalisation, growth of titanium-oxo-phosphate clusters and remov…

2019

Controlled cellulose disassembly affords many variants including amorphous micro-sized cellulose crystals (MCC) and cellulose nano-sized crystals (CNC), which have emerged recently as green and sustainable nanomaterials. Unfortunately, their lower reactivity and thermal and chemical instability constitute an impediment for multifaceted nanoscience and nanotechnology usage. Herein, MCC and CNC are functionalised using two phosphorus derivatives (phosphoryl chloride and hexachlorocyclotriphosphazene), under acid-free, urea-free and corrosive-free, gentle experimental conditions. Notably, CNC can accommodate more phosphorus species compared to MCC, with the bulky phosphazene precursor being le…

Optical suppression of ferroelectricity in polysiloxane copolymers with chiral and photochromic side groups

1998

The ferroelectricity of surface-stabilized aligned films of polysiloxane copolymers containing chiral esters and photochromic azobenzene moieties within the side groups is suppressed on UV irradiation and is rebuilt on visible irradiation. The liquid crystalline polymer (Sc* 64 SA 80 i) shows ferroelectric behavior below 64°C. The photoinduced modification of supramolecular order and the corresponding changes in its dynamics are studied by polarized UV/vis spectroscopy and broad band dielectric spectroscopy (10−2–105 Hz). The dielectric measurements show that UV irradiation causes a loss of ferroelectricity within an interval of 10 K below the phase transition temperature. The photochemical…

A theoretical study of the lowest electronic states of azobenzene: the role of torsion coordinate in the cis-trans photoisomerization

2003

In the present paper we report the results of a multiconigurational computational study on potential- energy curves of azobenzene along the NN twisting to clarify the role of this coordinate in the decay of the S2(pp*) and S1(np*) states. We have found that there is a singlet state, S3 at the trans geometry, on the basis of the doubly excited coniguration n 2 p* 2 , that has a deep minimum at about 90 of twisting, where it is the lowest excited singlet state. The existence of this state provides an explanation for the short lifetime of S2(pp*) and for the wavelength-dependence of azobenzene photochem- istry. We have characterized the S1(np*) state by calcu- lating its vibrational frequencie…

Photochemical formation of [4.4.4](1,3,5)cyclophanes from 1,3,5-tris(3-phenylpropenoyl)benzenes

2004

Abstract Irradiation of 1,3,5-tris(3-phenylpropenoyl)benzene ( 1a ) yields in solution a dimer 2a by a threefold head-to-head/anti [2π+2π]cycloaddition. The stereochemistry of this [4.4.4](1,3,5)cyclophane was determined by 1H and 13C NMR studies including NOE measurements and a calculation of the AA′MM′ spin pattern of the methine protons. In contrast to the solution photochemistry, which is presumably controlled by the arrangement of an excimer, the irradiation in the crystalline state leads by a topochemical control to a dimer 3a , which contains a single four-membered ring.

Highlights of metal ion-based photochemical switches

2014

Abstract Selected metal complexes behaving as photochemical switches, mostly operating by light emission/absorption without the intervention of any added chemical species, are reviewed. First, the switching mechanisms are analyzed to offer readers an easier understanding of the described systems. Examples of photochemical switching based on complexation/decomplexation processes and photo-bistable systems, comprising metal complexes with azobenzene, azopyridine, diarylethene, spirocyclic and rhodamine ligands, make the central body of the review. These examples were chosen to provide an overview of the evolution of metal-ion based photochemical switches, collecting together historical cases …