Ciencia y Tecnología
Factorization in spin systems under general fields and separable ground-state engineering
Cerezo de la Roca, Marco Vinicio Sebastian; Rossignoli, Raúl Dante; Canosa, Norma Beatriz
We discuss ground-state factorization schemes in spin S arrays with general quadratic couplings under general magnetic fields, not necessarily uniform or transverse. It is shown that, given arbitrary spin alignment directions at each site, nonzero XYZ couplings between any pair and fields at each site always exist such that the ensuing Hamiltonian has an exactly separable eigenstate with the spins pointing along the specified directions. Furthermore, by suitable tuning of the fields this eigenstate can always be cooled down to a nondegenerate ground state. It is also shown that in open one-dimensional systems with fixed arbitrary first-neighbor couplings at least one separable eigenstate compatible with an arbitrarily chosen spin direction at one site is always feasible if the fields at each site can be tuned. We demonstrate as well that in the vicinity of factorization, i.e., for small perturbations in the fields or couplings, pairwise entanglement reaches full range. Some noticeable examples of factorized eigenstates are unveiled. The present results open the way for separable ground-state engineering. A notation to quantify the complexity of a given type of solution according to the required control on the system couplings and fields is introduced.
Conditional purity and quantum correlation measures in two qubit mixed states
Conditional purity and quantum correlation measures in two qubit mixed states
Rebón, Lorena; Rossignoli, Raúl Dante; Varga, Juan José Miguel; Gigena, Nicolás Alejandro; Canosa, Norma Beatriz; Iemmi, Claudio César; Ledesma, Silvia Adriana
We analyze and show experimental results of the conditional purity, the quantum discord and other related measures of quantum correlation in mixed two-qubit states constructed from a pair of photons in identical polarization states. The considered states are relevant for the description of spin pair states in interacting spin chains in a transverse magnetic field. We derive clean analytical expressions for the conditional local purity and other correlation measures obtained as a result of a remote local projective measurement, which are fully verified by the experimental results. A simple exact expression for the quantum discord of these states in terms of the maximum conditional purity is also derived.
Social modulation of the daily activity rhythm in a solitary subterranean rodent, the tuco-tuco (Ctenomys sp)
Social modulation of the daily activity rhythm in a solitary subterranean rodent, the tuco-tuco (Ctenomys sp)
Tomotani, Barbara Mizumo; Amaya, Juan Pablo; Oda, Gisele Akemi; Valentinuzzi, Verónica Sandra
South American subterranean rodents are mainly described as solitary and mutual synchronization was never observed among individuals maintained together in laboratory. We report that a single birth event was capable of disrupting the robust nocturnal activity rhythm of singly housed tuco-tucos from north-west Argentina. "Around-the-clock activity" was displayed by 8 out of 13 animals whose cages were closer to the newborn pups. However, experimental exposure to a pup vocalization did not produce a similar effect on the rhythms of adult animals. Our results indicate an effect of social interaction in the expression of biological rhythms even in solitary animals.
La reciprocidad discontinua en español
La reciprocidad discontinua en español; Discontinuous reciprocity in Spanish
Mare, María de Los Angeles
Una de las lecturas que desencadena la presencia del clítico se en español es la recíproca. A diferencia de la lectura reflexiva, la interpretación recíproca se obtiene únicamente cuando el clítico se vincula a una expresión plural, sea un plural morfológico o sintáctico (i.e., una coordinación). Sin embargo, la presencia de un sintagma comitativo favorece la lectura recíproca aún si la expresión con la que se relaciona el clítico está en singular (Astérix se abrazó con Obélix). Este fenómeno se denomina reciprocidad discontinua (Dimitriadis 2000 y trabajos posteriores) y ha sido estudiado principalmente en las lenguas eslavas. Nuestro objetivo es revisar las características de esta construcción en español y determinar, por un lado, cómo se vincula el sintagma comitativo con el resto de la estructura y, por el otro, cuál es el estatuto del clítico se. A partir de estas discusiones proponemos un análisis en el marco de la Gramática Generativa que permite dar cuenta de las propiedades de ciertos sintagmas preposicionales y de las consecuencias del ensamble de éstos en la estructura general.; One of the readings of the clitic ‘se’ in Spanish is the one related to reciprocity. This interpretation differs from the reflexive one in that the first is obtained only when the clitic relates to a plural expression, no matter if it is a morphological plural or a syntactic one (i.e., a coordination). However, the presence of a comitative phrase favors the reciprocity interpretation, even when the expression associated with the clitic is singular (Astérix se abrazó con Obélix Lit. ‘AstérixSG CLSG hugged with Obélix’- ‘Astérix and Obélix hugged each other’). This phenomenon has been called discontinuous reciprocity (Dimitriadis 2000 and subsequent work) and it has been mainly studied for Slavic languages. Our main goal is to revise the properties of this construction in Spanish in order to define, on the one hand, how the comitative phrase relates to the main structure, and on the other, which is the clitic se status. Based on those aspects we propose an analysis framed in Generative Grammar which lets us explain the properties of comitative prepositional phrases and the consequences of their merge in the
structure.
Pedagogical Cues to an Artist’s Intention in Young Children’s Understanding of Drawings
Pedagogical Cues to an Artist’s Intention in Young Children’s Understanding of Drawings
Salsa, Analía Marcela; Vivaldi, Romina
Three studies investigated the effects of pedagogical cues to an artist’s referential intention on 2- and 2.5-year-old children’s understanding of drawings in a matching task without verbal labels support. Results showed that pedagogical cues, the combination of the artist’s eye gaze while she was creating the drawings (nonlinguistic cues), and verbal descriptions about her graphic actions (linguistic cues) enabled 2-year-olds to match highly realistic line drawings with referents. However, 2-year-olds’ performance was not influenced to an equal degree by nonlinguistic and linguistic cues; verbal scripts appeared to be the critical aspect of pedagogical demonstration even with predrawn pictures. By contrast, at 2.5 years of age, children inferred the artist’s intention when comprehending drawings in the absence of pedagogical cues. This research illustrates the potential power of pedagogical demonstration to communicate referential intentions in the pictorial symbol domain.
Performance of ZnSe(Te) as fiberoptic dosimetry detector
Performance of ZnSe(Te) as fiberoptic dosimetry detector
Ramírez, M.; Martínez Clemente, Nahuel Facundo; Marcazzo, Salvador Julian; Molina, Pablo Fernando; Feld, D.; Santiago, Martin Alejo
Fiberoptic dosimetry (FOD) is an experimental technique suitable for in-vivo, real time dosimetry in radiotherapy treatments. FOD relies on using a small scintillator coupled to one end of a long optical fiber. The scintillator is placed at the point where the dose rate is to be determined whereas a light detector at the other end of the fiber measures the intensity of the radioluminescence emitted by the scintillator. One of the problems hampering the straightforward application of this technique in clinics is the presence of Cherenkov radiation generated in the fiber by the ionizing radiation, which adds to the scintillating light and introduces a bias in the dose measurement. Since Cherenkov radiation is more important in short wavelength range of the visible spectrum, using red-emitting scintillators as FOD detectors permits to reduce the Cherenkov contribution by using optical filters. In this work, the performance of red-emitting tellurium-doped zinc selenide crystal as FOD detector is evaluated and compared to the response of an ion-chamber.
On the instability of two entropic dynamical models
On the instability of two entropic dynamical models
Henry, Guillermo Sebastian; Rodriguez, Daniela Andrea
In this paper we study two entropic dynamical models from the viewpoint of information geometry. We study the geometry structures of the associated statistical manifolds. In order to analyse the character of the instability of the systems, we obtain their geodesics and compute their Jacobi vector fields. The results of this work improve and extend a recent advance in this topics studied in Peng et al.[13].
Performance of a PCR assay for the rapid identification of the Klebsiella pneumoniae ST258 epidemic clone in Latin American clinical isolates
Performance of a PCR assay for the rapid identification of the Klebsiella pneumoniae ST258 epidemic clone in Latin American clinical isolates
Gómez, Sonia Alejandra; Rapoport, Mario Daniel; Piergrossi, N.; Faccone, Diego Francisco; Pasteran, Fernando; de Belder, Denise Gisele; ReLAVRA-Group; Petroni, A.; Corso, A.
The worldwide dissemination of Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae ST258 demands a rapid PCR-based typing method to detect unique genes of the ST258 clone. This study evaluates a PCR developed by Adler et al. (2014) for the detection of ST258 in K. pneumoniae clinical isolates centered on the identification of the pilv-I and prp genes. We tested 143 clinical isolates from Argentina (n = 109), Chile (n = 1), Colombia (n = 1), Costa Rica (n = 2), Ecuador (n = 5), El Salvador (n = 2), Nicaragua (n = 5), Panamá (n = 2), Paraguay (n = 2), Perú (n = 3) and Trinidad and Tobago (n = 11) recovered from 2006 to 2015. blaKPC, pilv-l and prp genes were detected by PCR and sequenced by standard procedures. ST258 and non-ST258 were defined by PFGE and/or MLST. Isolates were grouped according to PFGE patterns: 58 were compatible with ST258 (group 1) and 85 with non-ST258 (group 2). MLST study was done on an arbitrary selection of isolates. The pilv-l gene was present only in ST258 isolates, regardless of the presence of the blaKPC gene. Results for the prp gene were variable. Its presence did not define ST258. The pilv-I PCR had a sensitivity and specificity of 100%, respectively, for the detection of ST258 in the isolates under investigation. Given our findings, the pilv-I PCR could replace more time and resource consuming methods, allowing for more rapid detection of the circulating high risk K. pneumoniae clone ST258 in Latin American (LA) countries.
Synthesis, characterization and activity of imidazolate-bridged and Schiff-base dinuclear complexes as models of Cu,Zn-SOD. A comparative study
Synthesis, characterization and activity of imidazolate-bridged and Schiff-base dinuclear complexes as models of Cu,Zn-SOD. A comparative study
Daier, Veronica Andrea; Rivière, Eric; Mallet Ladeira, Sonia; Moreno, Diego Martin; Hureau, C; Signorella, Sandra Rosanna
Two imidazolate-bridged diCuII and CuIIZnII complexes, [CuZn(dien)2(μ-Im)](ClO4)3·MeOH (1) and [Cu2(dien)2(μ-Im)](ClO4)3 (2) (Im = imidazole, dien = diethylenetriamine), and two complexes formed with Schiff base ligands, [CuZn(salpn)Cl2] (3) and [Cu2(salbutO)ClO4] (4) (H2salpn = 1,3-bis(salicylidenamino)propane, H3salbutO = 1,4-bis(salicylidenamino)butan-2-ol) have been prepared and characterized. The reaction of [Cu(dien)(ImH)](ClO4)2 with [Zn(dien)(H2O)](ClO4)2 at pH ≥ 11 yields complex 1; at lower pH, the Cu3Zn tetranuclear complex [{(dien)Cu(μ-Im)}3Zn(OH2)(ClO4)2](ClO4)3 (1a) forms as the main reaction product. X-ray diffraction of 1a reveals that the complex contains a metal centered windmill-shaped cation having three blades with a central Zn ion and three peripheral capping Cu(dien) moieties bound to the central Zn ion through three imidazolate bridges. The four complexes are able to disproportionate O2− in aqueous medium at pH 7.8, with relative rates 4 > 1 > 2 ≫ 3. [Cu2(salbutO)]+ (4) is the most easily reducible of the four complexes and exhibits the highest activity among the SOD models reported so far; a fact related to the ligand flexibility to accommodate the copper ion in both CuI and CuII oxidation states and the lability of the fourth coordination position of copper facilitating stereochemical rearrangements.
A high temperature study on thermodynamic, thermal expansion and electrical properties of BaCe0.4Zr0.4Y0.2O3−δ proton conductor
A high temperature study on thermodynamic, thermal expansion and electrical properties of BaCe0.4Zr0.4Y0.2O3−δ proton conductor
Basbus, Juan Felipe; Arce, Mauricio Damián; Prado, Fernando Daniel; Caneiro, Alberto; Mogni, Liliana Verónica
BaCe0.4Zr0.4Y0.2O3−δ (BCZY) was synthesized by solid state reaction, calcined and sintered at 1600 °C for 12 h. Crystal structure was studied by X-ray diffraction (XRD). Morphology and porosity were determined by scanning electron microscopy (SEM). Crystalline structure, oxygen non-stoichiometry, linear expansion and electrical conductivity were characterized under oxidizing and reducing atmosphere by high temperature X-ray diffraction (HT-XRD), thermogravimetry (TG), dilatometry, and electrochemical impedance spectroscopy (EIS), respectively. Chemical stability under CO2-rich atmosphere was evaluated by TG. BCZY electrical conductivity was studied by EIS under O2-containing atmosphere with water vapor (2% H2O) and heavy water vapor (2% D2O) in order to evaluate protonic conductivity. Throughout these techniques, interstitial proton incorporation/loss was observed under oxidizing and reducing atmosphere, between 300 and 500 °C. The conductivity presents two contributions. The bulk conductivity at high frequencies takes the same value regardless wet oxidizing or reducing atmosphere, decreasing its value in presence of D2O vapor supporting H-conductivity. On the other hand, the grain boundary conductivity was strongly dependent on the nature of wet atmosphere.
Micro and nanoparticles of native and modified cassava starches as carriers of the antimicrobial potassium sorbat
Micro and nanoparticles of native and modified cassava starches as carriers of the antimicrobial potassium sorbat
Alzate Calderón, Paola Carolina; Zalduendo, María Mercedes; Gerschenson, Lia Noemi; Flores, Silvia Karina
Cross-linked and/or acetylated cassava starches were synthesized and characterized. The acetylation increased the water retention capacity and the solubility in water while the higher level of cross-linking produced the opposite effect on starch. Native (NCS) and acetylated cassava starches (ACS) were used to generate starch micro- and nanoparticles by the dialysis technique.The nanoparticle fraction was around 1.8 g 100 g1 and 12 g 100 g1 (starch dry basis) for NCS and ACS, respectively. The nanoparticle sizes were around 23?255nm with zeta potential extending from 4 to 44mV, while the microscopic fractions ranged 5?87mm. In addition, the capacity of particles to support potassium sorbate (KS) was tested. NCS and ACS particles supported a similar quantity of KS (1400 ppm) and the presence of antimicrobial decreased the particle size for NCS. The precipitation in ethanol technique was also used to generate microparticles where the particles generated from acetylated starches were smaller (8?58mm) than those from native ones (30?227 mm). The KS content that these particles could incorporate was around 2020 ppm. The applied technique modulated the average dimension of the particles obtained, as well as the antimicrobial retention capacity. These innovative materials could bepotentially helpful for shelf life extension by the contribution to the KS stabilization to be incorporated in the bulk of food products.
Análisis polínico de mieles inmaduras en el sector oeste de las yungas de Jujuy (Argentina)
Análisis polínico de mieles inmaduras en el sector oeste de las yungas de Jujuy (Argentina)
Méndez, Magalí Verónica; Sánchez, Ana Carina; Flores, Fabio Fernando; Lupo, Liliana Concepcion
Con el objetivo de conocer los recursos nectaríferos utilizados por Apis mellifera L. en el sector oeste de las Yungas, se examinaron 14 muestras de miel inmadura y dos de miel madura correspondientes a los períodos apícolas 2011?2012 y 2012?2013, pertenecientes a un apiario de la localidad de Tilquiza (Jujuy). Las muestras fueron procesadas de acuerdo a las técnicas melisopalinológicas convencionales con posterior acetólisis. Se identificaron un total de 53 tipos polínicos pertenecientes a 31 familias botánicas, siendo las familias con mayor riqueza polínica Asteraceae y Fabaceae. Se identificaron como recursos dominantes a Crinodendron tucumanum en setiembre de 2011, Blepharocalyx salicifolius en noviembre y diciembre de 2011 y al tipo Scutia/Condalia en octubre de 2012. Como aportes secundarios se registraron a Allophylus edulis, Zanthoxylum, Parapiptadenia excelsa, Baccharis, Gnaphalium, Eucalyptus y tipo Cissus, destacándose la influencia de la flora nativa de las Yungas. A partir de este estudio se pudo conocer la dinámica del ingreso de néctar a la colmena y valorar aquellos recursos que no se encuentran presentes en las mieles maduras y que son de importancia para el desarrollo de la colmena.
Memorias y usos públicos del pasado en torno a la "lucha antisubversiva": Notas sobre Carlos Sacheri y Jordán Bruno Genta
Memorias y usos públicos del pasado en torno a la "lucha antisubversiva": Notas sobre Carlos Sacheri y Jordán Bruno Genta; Memories and public uses of the past throughout the “antisubversive struggle”: Notes about Carlos Sacheri and Jordán Bruno Genta
Cersósimo, Facundo
En 1974 fueron asesinados en la vía pública Jordán Bruno Genta y Carlos Alberto Sacheri. Para la época ambos intelectuales eran referentes de sectores nacionalistas y católicos que en el convulsionado escenario político argentino promovieron la necesidad de la “lucha antisubversiva”. A partir de reconstruir los diversos usos públicos de los que fueron objeto luego de sus asesinatos, el presente artículo estudia el proceso de elaboración de las memorias alternativas que buscaron legitimar la actuación represiva de las Fuerzas Armadas tras el retorno de la democracia en 1983. Al final del artículo también se reflexionará acerca del lugar del historiador al momento abordar aquellos fragmentos del pasado marcados por la violencia política, y que fueron recortados y descontextualizados para ser utilizados en los combates memoriales analizados.; In 1974 where murdered in the public space Jordan Bruno Genta y Carlos Alberto Sacheri. By the time both intelectuals were an important reference of nationalists and catholic groups that, in the agitated political scenario of Argentina, promoted the need of an “antisubversive struggle”. As from the reconstruction of the different public wich they were subject, the present article studies the process of elaboration of alternative memories wich seek to legitimate the repressive action of the Armed Forces after the return of Democracy at 1983. At the closing of the article is also a reflection about the role of the historian at the moment of analyze those fragments of the past signed by the political violence, wich were trimmed and decontextualized to be used in the memorial combats analyzed.
Nuclear Magnetic Resonance Relaxation Studies in Shale
Nuclear Magnetic Resonance Relaxation Studies in Shale
Ramia, Maximo Elias; Martín, C. A.
The present work involves a comprehensive experimental study of proton (1 H) nuclear magnetic resonance (NMR) transversal relaxation in shale. The sample studied belongs to the “Vaca Muerta” formation of the Neuquén basin, Argentina. The results show that the relaxation process is governed by anomalous diffusion processes in micro-pores. These processes result from the combination of interactions between the liquid molecules and the pore walls, whose structure is characterized by both large tortuosity and abundance of paramagnetic impurities, giving rise to local strong time-dependent magnetic field gradients. In addition, a simultaneous experimental method of data fitting is presented which allows processing all the relaxation profiles within a single time domain. Thus, yielding results univocally related to the complete set of relaxation data.
The UVB1 Vitamin D Analogue Inhibits Colorectal Carcinoma Progression
The UVB1 Vitamin D Analogue Inhibits Colorectal Carcinoma Progression
Ferronato, María Julia; Alonso, Eliana Noelia; Gandini, Norberto Ariel; Fermento, María Eugenia; Villegas, María Emilia; Quevedo, Mario Alfredo; Arevalo, Julian; López Romero, Alejandro; Rivadulla, Marcos Lois; Gómez, Generosa; Fall, Yagamare; Facchinetti, Maria Marta; Curino, Alejandro Carlos
Vitamin D has been shown to display a wide variety of antitumour effects, but their therapeutic use is limited by its severe side effects. We have designed and synthesized a Gemini vitamin D analogue of calcitriol (UVB1) which has shown to display antineoplastic effects on different cancer cell lines without causing hypercalcemia. The aim of this work has been to investigate, by employing in silico, in vitro, and in vivo assays, whether UVB1 inhibits human colorectal carcinoma progression. We demonstrated that UVB1 induces apoptotic cell death and retards cellular migration and invasion of HCT116 colorectal carcinoma cells. Moreover, the analogue reduced the tumour volume in vivo, and modulated the expression of Bax, E-cadherin and nuclear β-catenin in tumour animal tissues without producing toxic effects. In silico analysis showed that UVB1 exhibits greater affinity for the ligand binding domain of vitamin D receptor than calcitriol, and that several characteristics in the three-dimensional conformation of VDR may influence the biological effects. These results demonstrate that the Gemini vitamin D analogue affects the growth of the colorectal cancer and suggest that UVB1 is a potential chemotherapeutic agent for treatment of this disease.
Fever-range hyperthermia improves the anti-apoptotic effect induced by low pH on human neutrophils promoting a proangiogenic profile
Fever-range hyperthermia improves the anti-apoptotic effect induced by low pH on human neutrophils promoting a proangiogenic profile
Erra Diaz, Fernando Alberto; Dantas, Ezequiel Carlos; Cabrera, Maia Diana Eliana; Arriola Benitez, Paula Constanza; Delpino, María Victoria; Duette, Gabriel; Rubione, Julia; Sanjuan, Norberto Aníbal; Trevani, Analía Silvina; Geffner, Jorge Raúl
Neutrophils have the shortest lifespan among leukocytes and usually die via apoptosis, limiting their deleterious potential. However, this tightly regulated cell death program can be modulated by pathogen-associated molecular patterns (PAMPs), danger-associated molecular pattern (DAMPs), and inflammatory cytokines. We have previously reported that low pH, a hallmark of inflammatory processes and solid tumors, moderately delays neutrophil apoptosis. Here we show that fever-range hyperthermia accelerates the rate of neutrophil apoptosis at neutral pH but markedly increases neutrophil survival induced by low pH. Interestingly, an opposite effect was observed in lymphocytes; hyperthermia plus low pH prevents lymphocyte activation and promotes the death of lymphocytes and lymphoid cell lines. Analysis of the mechanisms through which hyperthermia plus low pH increased neutrophil survival revealed that hyperthermia further decreases cytosolic pH induced by extracellular acidosis. The fact that two Na+/H+ exchanger inhibitors, 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and amiloride, reproduced the effects induced by hyperthermia suggested that it prolongs neutrophil survival by inhibiting the Na+/H+ antiporter. The neutrophil anti-apoptotic effect induced by PAMPs, DAMPs, and inflammatory cytokines usually leads to the preservation of the major neutrophil effector functions such as phagocytosis and reactive oxygen species (ROS) production. In contrast, our data revealed that the anti-apoptotic effect induced by low pH and hyperthermia induced a functional profile characterized by a low phagocytic activity, an impairment in ROS production and a high ability to suppress T-cell activation and to produce the angiogenic factors VEGF, IL-8, and the matrix metallopeptidase 9 (MMP-9). These results suggest that acting together fever and local acidosis might drive the differentiation of neutrophils into a profile able to promote both cancer progression and tissue repair during the late phase of inflammation, two processes that are strongly dependent on the local production of angiogenic factors by infiltrating immune cells.
Very fast dissolving acid carboxymethylcellulose-rifampicin matrix: development and solid-state characterization
Very fast dissolving acid carboxymethylcellulose-rifampicin matrix: development and solid-state characterization
Luciani Giacobbe, Laura Carolina; Ramírez Rigo, María Veronica; Garro Linck, Yamila; Monti, Gustavo Alberto; Manzo, Ruben Hilario; Olivera, Maria Eugenia
One of the main obstacles to the successful treatment of tuberculosis is the poor and variable oral bioavailability of rifampicin (RIF), which is mainly due to its low hydrophilicity and dissolution rate. The aim of this work was to obtain a hydrophilic new material that allows a very fast dissolution rate of RIF and therefore is potentially useful in the development of oral solid dosage forms. The acid form of carboxymethylcellulose (CMC) was co-processed with RIF by solvent impregnation to obtain CMC-RIF powder, which was characterized by polarized optical microscopy, powder x-ray diffraction, DSC-TGA, hot stage microscopy, 13C and 15N solid-state NMR and FT-IR spectroscopy. In addition, the CMC-RIF matrices were subjected to water uptake and dissolution studies to assess hydrophilicity and release kinetics. CMC-RIF is a crystalline solid dispersion. Solid-state characterization indicated that no ionic interaction occurred between the components, but RIF crystallized as a zwitterion over the surface of CMC, which drastically increased the hydrophilicity of the solid. The CMC-RIF matrices significantly improved the water uptake of RIF and disintegrated in a very short period immediately releasing RIF. As CMC improves the hydrophilicity and delivery properties of RIF, CMC-RIF is very useful in the design of oral solid dosage forms with very fast dissolution of RIF, either alone or in combination with other antitubercular drugs.
Kinetic of the thermal decomposition of disubstituted tetroxanes
Kinetic of the thermal decomposition of disubstituted tetroxanes
Bordón, Alexander Germán; Pila, Andrea Natalia; Jorge, María Cristina; Jorge, Lilian Cristina; Profeta, Mariela Inés; Romero, Jorge Marcelo; Jorge, Nelly Lidia
The thermal decomposition of diphenyl diperoxide (DFT) and dibutanal diperoxide (DPG) were investigated over the temperature range 130 to 166°C. They were found to be first order with a high degree of conversion (60%). Arrhenius parameters were calculated: activation energy, 108 kJ mol-1 and pre-exponential factor, 6.5 109 s -1 for DFT and 80.8 kJ mol-1 and pre-exponential factor, 1.8 109 s - 1 for DPG. The principle decomposition products were aldehyde (about 1.9 mole per mole DFT and 2.0 mole per mole DPG) and oxygen molecule. All observations were interpreted in terms of decomposition pathways initiated by O-O homolysis. The corresponding activation parameters for the reaction of DFT in methanol (ΔH0# = 103.8 ± 3.3 kJ mol-1 ; ΔS0# = -69.9 ± 7.5 J mol-1 K -1 ; ΔG0# = 133.1 ± 3.3 kJ mol-1) were compared with values obtained for PDG thermolysis in the same solvents (ΔH0# = 75.4 ± 2.9 kJ mol-1 ; ΔS0# = -189.2 ± 2.5 J mol-1 K -1 ; ΔG0# = 157.4 ± 2.9 kJ mol-1). Furthermore, the pertinent substituent effect on the peroxidic bond strength of those molecules in solution was evaluated.
Prórroga de ANR P+L 2016 C2
El Fondo Tecnológico Argentino informa que se ha prorrogado la fecha límite para la presentación de propuestas de la convocatoria ANR P+L 2016 C2.
Nanociencia: la alquimia de los materiales
Un equipo de investigadores del Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas de la Universidad Nacional de La Plata realizó importantes aportes en el estudio de nanomateriales para las áreas de energía y de salud. El trabajo a escala nanométrica permite potenciar las propiedades y mejorar la eficiencia de los materiales.
Páginas
