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Publications
Publications (140)
The Parque Nacional La Campana (PNLC) was recently recognized for its high soil surface microbial richness. Here, we explored the microbial community structure in soil profiles from contrasting facing slopes where sclerophyllous forest (SF) and xerophytic shrubland (XS) develop. Soil physicochemical conditions (dry density, pH, and organic matter C...
Wildfires and drought stressors can significantly limit forest recovery in Mediterranean-type ecosystems. Since 2010, the region of central Chile has experienced a prolonged Mega Drought, which intensified into a Hyper Drought in 2019, characterized by record-low precipitation and high temperatures, further constraining forest recovery. This study...
The interplay between wildfires and drought stress has significantly limited forest recovery in the Mediterranean ecosystem of central Chile. Since 2010, the region has faced a prolonged 'Mega Drought,' which intensified into a 'Hyper Drought' in 2019, with record-low precipitation and high temperatures, further constraining forest recovery amidst...
Parque Nacional La Campana (PNLC) is recognized worldwide for its flora and fauna, rather than for its microbial richness. Our goal was to characterize the structure and composition of microbial communities (bacteria, archaea and fungi) and their relationship with the plant communities typical of PNLC, such as sclerophyllous forest, xerophytic shru...
Wild pollinators play a crucial role in maintaining healthy ecosystems and sustaining agricultural productivity. However, their survival is at risk due to habitat loss and land use changes, exacerbating the ongoing biodiversity crisis, and jeopardising global food security. We assessed the contribution of native vegetation cover to pollination and...
Este trabajo presenta nuevo registro sedimentológico y palinológico que reconstruye la historia ambiental durante la transición del Holoceno medio a tardío en el centro sur de Chile (34°-38°S). El sitio de estudio corresponde a un pequeño humedal llamado Laguna Verde (36º47’S, 73º09’W; 22 m s.n.m.; ~4 ha), el cual se emplaza en una micro-cuenca (13...
The Anthropocene is an uneven phenomenon. Accelerated shifts in the functioning of the Earth System are mainly driven by the production and consumption of wealthy economies. Social, environmental and health costs of such industrialization, however, bear on low-income communities inhabiting severely degraded territories by polluting activities (i.e....
Chile Central (30° - 37°S), concentra cerca del 75% de la población total del país, lo cual se traduce en una enorme demanda hídrica. Gran parte del agua disponible del área en cuestión proviene de la nieve estacional y los glaciares ubicados en la alta cordillera. En este contexto, el cambio climático se emplaza como una amenaza para la seguridad...
Northern Chile harbors different bioclimatic zones including hyper-arid and arid ecosystems and hotspots of microbial life, such as high altitude wetlands, which may contribute differentially to greenhouse gases (GHG) such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). In this study, we explored ground level GHG distribution and th...
The degree to which vegetation and site type have influenced fire regimes through the Holocene has not been investigated in detail in the temperate ecosystems of southern Patagonia. Here we present a first attempt using a paired-basin approach to study the evolution of fire regimes in sectors dominated by humid Nothofagus forests and the xeric Pata...
Subduction, isostatic rebound, and changes in global sea levels, combined with the last glaciation, have shaped the geography of the channels of Western Patagonia. Current archaeological research in this area includes some ten sites that allow us to characterize the occupation of this territory by marine hunter-gatherers. The studied archaeological...
Este libro busca fomentar el conocimiento sobre el alto valor ecológico del Santuario de
la Naturaleza Laguna El Peral, humedal natural de la Región de Valparaíso, que es el más
importante atractivo turístico de la comuna de El Tabo. El alto valor ecológico que posee, es
principalmente por su biodiversidad e hidrogeología, además del cultural, soci...
Subduction, isostatic rebound, and changes in global sea levels, combined with the last glaciation, have shaped the geography of the channels of Western Patagonia. Current archaeological research in this area includes some ten sites that allow us to characterize the occupation of this territory by marine hunter-gatherers. The studied archaeological...
The Carpathian Mountains were one of the main mountain reserves of the boreal and cool temperate flora during the Last Glacial Maximum (LGM) in East-Central Europe. Previous studies demonstrated late glacial vegetation dynamics in this area; however, our knowledge on the LGM vegetation composition is limited due to the scarcity of suitable sediment...
Along the Chilean–Peruvian coast, numerous archaeological sites associated with shell accumulations provide evidence for the role of coastal environments as a natural corridor for the human occupation of South America. In particular, the semi-arid coastline of northern Central Chile (∼33–27° S) is a key area for investigating the relationship betwe...
The geometry and harmonic frequencies of naphthalene, azulene, phenanthrene, and anthracene have been computed using the Becke three-parameter Lee-Yang-Parr functional (B3LYP) and basis sets of spd and spdf quality. A simple scaling procedure for the harmonic frequencies is proposed that brings computed harmonics to within 10-20 cm(-1) or better of...
The position and intensity of the southern westerly wind belt varies seasonally as a consequence of changes in sea surface temperature. During the austral winter, the belt expands northward and the wind intensity in the core decreases. Conversely, during the summer, the belt contracts, and the intensity within the core is strengthened. Reconstructi...
A suite of mechanisms has been proposed to account for natural variations in atmospheric CO2 during the Holocene; all of which have achieved limited success in reproducing the timing, direction, and magnitude of change. Recent modeling studies propose that changes in the latitudinal position and strength of the Southern Hemisphere Westerly Winds (S...
The position and intensity of the southern westerly wind belt varies seasonally as a consequence of changes in sea surface temperature. During the austral winter, the belt expands northward and the wind intensity in the core decreases. Conversely, during the summer, the belt contracts, and the intensity within the core is strengthened. Reconstructi...
Paleoclimate records from southern South America can be used to address important questions regarding the timing and nature
of late-Holocene climate variability. During the last 30 years, many areas of southern South America have experienced rapid
climatic and ecological changes that are driven by global and hemispheric-scale ocean-atmosphere proce...
Resolving the timing, direction, and magnitude of paleoclimate changes in the southern midlatitudes is a prerequisite for determining the mechanisms underlying abrupt and widespread climate changes between the hemispheres during the Last Glacial-Interglacial transition (LGIT). This issue is still debated, with previous studies producing apparently...
Here we report results from a high-resolution palynological record and stratigraphic/geochronologic data related to a Neoglacial event in Torres del Paine National Park, southern Chile (51°S, 71°W), to investigate climatic variations in Southwest Patagonia during the last 5000 years. The record reveals a stepwise expansion of Nothofagus-dominated w...
En esta tesis se desarrolló un registro de polen y carbón a una alta resolución temporal (45 y 20 años entre muestras, respectivamente) a partir de sedimentos lacustres provenientes de Lago Guanaco (51˚52’S-72˚52’W, 180 m.s.n.m.), ubicado en el ecotono bosque-estepa, al interior del Parque Nacional Torres del Paine. El propósito de esta tesis fue r...
The southern westerly winds are an important feature of atmospheric circulation in the mid- to high-latitudes of the Southern Hemisphere. Recent observations and model-based studies have shown that both the latitudinal position and the overall strength of the wind field can directly influence Southern Ocean circulation and have important implicatio...
The Southern Hemisphere westerly winds influence the spatial distribution of precipitation in southern South America and play a significant role in the global carbon cycle, yet little is known about how this important atmospheric circulation feature has varied in the past. Here, we present a sediment core record of late Holocene variability from La...
The quartic force fields of FNO and ClNO have been computed at the CCSD(T)/cc-pVTZ level. Using an
“augmented” basis set dramatically improves results for FNO but has no significant effect for ClNO. The
best computed force field for FWO yields harmonic frequencies and fundamentals in excellent agreement
with experiment. Overall, the force fields pr...
The mixed boron-nitrogen clusters B3N3 and B4N4 has been studied using augmented coupled-cluster methods. Both molecules have monocyclic ground state structures (1A1′ and 1A1g, respectively) with cumulenic-type equal bond lengths and alternating bond angles (BNB sharp, NBN blunt). The second most stable structures are linear BNBNBN(BN), with a 3Π g...
The anharmonic potential surface of NH2 has been computed ab initio using the quadratic configuration interaction method and large basis sets. The all-electron augmented coupled cluster surface with the [5s4p2d1f,3s2p] basis set reproduces the experimental fundamentals to within a few cm−1. For this quantitative agreement with experiment, both f fu...
The equilibrium bond length, harmonic frequency, first and second order anharmonicity constants, rotational and centrifugal distortion constants, as well as the rotation-vibrational and centrifugal coupling constants for the ground X2Σ+ and first excited A 2Π states of the SiN radical have been calculated at the complete active space SCF (CASSCF),...
The first spectral diffuse interstellar bands were observed as early as 1921, however, their origin is not entirely clarified even at present. Well over a hundred of these broad interstellar features have been listed in the visible and near-infrared spectral regions. It is probable that they come from more than one specific carrier, and various car...
The structure, infrared spectrum, and heat of formation of B2N, B2N−, BO, and B2O have been studied ab initio. B2N is very stable; B2O even more so. B2N, B2N−, B2O, and probably B2N+ have symmetric linear ground-state structures; for B2O, an asymmetric linear structure lies about 12 kcal/mol above the ground state. B2N+, B2N− and B2O have intense a...
A comprehensive study, throughout the valence region, of the electronic structure and electron momentum density distributions of the four conformational isomers of n-pentane is presented. Theoretical (e,2e) valence ionization spectra at high electron impact energies (1200 eV+electron binding energy) and at azimuthal angles ranging from 0 degrees to...
Inversion of the recently reported non-planar cyclic minimum-energy structure of C-8 (D2d symmetry) is studied by means of the second-order Moller-Plesset perturbation treatment with the 6-31G* basis set. Two new planar cyclic saddle points have been found, possessing D4h and C2h, symmetry and exhibiting two and one imaginary frequencies, respectiv...
The potential energy surface of the BN3 molecule has been explored using coupled cluster methods. It is shown unambiguously that the ground state is linear NNBN(1SIGMA+). Harmonic frequencies for B3N and BN3 have been computed using extended basis sets and coupled cluster methods including triple excitations (CCSD(T)). Computed frequencies and geom...
The structure and harmonic vibrations of BnNn clusters (n = 3-10) have been investigated using density functional theory with exact-exchange contributions. All structures are found to be cumulenic D-nh rings (equal bonds, alternating angles), with one intense out-of-plane mode and three infrared-active degenerate modes, of which the top one is extr...
Energetically low-lying states of the C2P and CNP molecular systems and their cations are studied. Geometries, harmonic frequencies, and dipole moments have been obtained at the density functional (using the Becke three-parameter Lee-Yang-Parr B3LYP functional) and coupled cluster theoretical levels in conjunction with correlation consistent basis...
The present study focuses on the low-lying valence electronically excited states of trans-stilbene. A comparison is made between semiempirical CIS-ZINDO/S and ab initio time-dependent density functional theory (TD-DFT) results obtained in conjunction with a cc-pVDZ basis set and using three different functionals, namely SVWN, B3LYP, and B3P86. Geom...
The potential energy surface of norbornane in its dicationic singlet ground state has been investigated in detail using density functional theory along with the nonlocal hybrid and gradient-corrected Becke three-parameter Lee-Yang-Parr functional (B3LYP) and the cc-pVDZ basis set. For the sake of more quantitative insight into the chemical reaction...
The main purpose of the present work is to predict from benchmark many-body quantum mechanical calculations the results of experimental studies of the valence electronic structure of dimethoxymethane employing electron momentum spectroscopy, and to establish once and for all the guidelines that should systematically be followed in order to reliably...
The westerly wind field is one of the most prominent atmospheric circulation features in the Southern Hemisphere and has a major impact on the climate of southern South America as well as Southern Ocean hydrography. Southernmost South America is well-located to investigate past changes in the westerly winds because regional precipitation variabilit...
The valence one-electron and shake-up ionization spectra of stella-2,6-diene, stella-2,6-dione, bicyclo-
[2.2.2]-octane-2,5-dione, and bicyclo-[2.2.1]-heptane-2,5-dione have been exhaustively studied, up to the double ionization
threshold and beyond, by means of one-particle Green’s function theory. This study is based on calculations
employing the...
The ionization bands and electron affinities of medium-size BnNn clusters (n = 3, 4, 5) have been investigated by means of one-particle Green's function calculations using the outer-valence Green's function (OVGF) approximation or the third-order algebraic diagrammatic construction [ADC(3)] scheme. Despite their structural similarity with isoelectr...
Calculations employing density functional theory indicate that, rather than undergoing fragmentation, dicationic clusters of benzene, hexafluorobenzene, and naphthalene produced by sequential one-electron or sudden double-ionization experiments on the neutrals can relax via the formation of inter-ring covalent C-C bonds, along with a series of prot...
The westerly wind field is one of the most prominent atmospheric circulation features in the Southern Hemisphere, which has a major impact on the climate of southern South America and hydrographic conditions in the Southern Ocean. Recent studies have argued that latitudinal shifts in the westerly boundaries during the LGM played a role in the modul...
We report on the results of an exhaustive study of the interplay between the valence electronic structure, the topology and reactivity of orbitals, and the molecular structure of biphenyl by means of Penning ionization electron spectroscopy in the gas phase upon collision with metastable He*(2 3S) atoms. The measurements are compared with one-parti...
Results of a study of the valence electronic structure of norbornene (C(7)H(10)), up to binding energies of 30 eV, are reported. Experimental electron momentum spectroscopy (EMS) and theoretical Green's function and density functional theory approaches were utilized in this investigation. A stringent comparison between the electron momentum spectro...
In continuation of a recent study of the electronic structure of norbornane [J. Chem. Phys., 2004, 121, 10525] by means of electron momentum spectroscopy (EMS), we present Green's Function calculations of the ionization spectrum of this compound at the ADC(3) level using basis sets of varying quality, along with accurate evaluations at the CCSD(T)...
The westerly wind field is one of the most prominent atmospheric circulation features in the Southern Hemisphere, having a major impact on the climate of Chile and hydrographic conditions in the Southern Ocean. The latitudinal position and strength of the westerlies directly influences the amount and isotopic composition of precipitation that falls...
We report on the results of an exhaustive study of the valence electronic structure of norbornane (C7H12), up to binding energies of 29 eV. Experimental electron momentum spectroscopy and theoretical Green’s function and density functional theory approaches were all utilized in this investigation. A stringent comparison between the electron momentu...
In the present contribution, we theoretically investigate the suitability of the sulfoxide route for the synthesis of conjugated polymers of relevance for the fabrication of low-band gap materials with improved characteristics. The study focuses specifically on the internal elimination (E(i)) reactions of sulfoxide precursors of model oligomers of...
The gas-phase internal elimination (E(i)) reaction of ethyl xanthate (CH(3)-CH(2)-S-CS-O-CH(3)) has been investigated by means of Hartree-Fock, second-order Møller-Plesset, and density functional theory (DFT) using the Becke three-parameter Lee-Yang-Parr (B3LYP) functional and the modified Perdew-Wang one-parameter model for kinetics (MPW1K). Consi...
In straightforward continuation of Green’s function studies of the ultraviolet photoelectron spectra of polycyclic aromatic compounds [Deleuze et al., J. Chem. Phys. 115, 5859 (2001); M. S. Deleuze, ibid. 116, 7012 (2002)], we present a benchmark theoretical determination of the ionization thresholds of benzene, naphthalene, anthracene, naphthacene...
The elimination and side reactions involved in the thermal conversion of sulfonyl precursor chains into poly(p-phenylene vinylene) (PPV) have been studied in detail, using Density Functional theory, along with the MPW1K functional. The performance of the MPW1K functional for describing radical dissociation and internal conversion reactions of sulfo...
In the present study, we investigate the influence of temperature on the width and location of bands in the UV−visible absorption spectra of oligomer chains of poly(p-phenylene vinylene) (PPV). These spectra have been computed by means of molecular dynamics (MD) simulations along with the classical MM3 force field, in conjunction with (Z)INDO/S-CIS...
The relative energies of stationary points on the potential energy surface of trans-stilbene have been accurately determined using Hartree–Fock, second and third-order Møller–Plesset (MP2, MP3), as well as Coupled Clusters theories with single and double excitations (CCSD), together with a perturbative estimate of connected triple excitations [CCSD...
Calculations using ab initio Hartree–Fock and Density Functional theories, the latter employing the B3LYP functional, in combination with a number of large standard basis sets ranging from 6-31G** to cc-pVDZ, have been performed on a series of ten and twelve vertex closo-carborane isomer species. Results obtained for optimized structural parameters...
The structural, rotational, and vibrational properties of Cn- clusters (n = 3−13) have been investigated by means of density functional theory (DFT/B3LYP) and, whenever possible, coupled cluster (CC) theory along with the aug-cc-pVDZ basis set. These properties are compared with those of their neutral counterparts and of the corresponding cations....
The gas-phase internal elimination (E(i)) reaction of the sulfoxide (-SO-CH(3)) precursors of ethylene and model oligomers of PPV and PITN has been investigated by means of Hartree-Fock, Møller-Plesset (second and fourth order), and Density Functional Theory (B3LYP, MPW1K) calculations. Considerable differences between the obtained ground state and...
The 1h (one-hole) and 2h-1p (two-hole; one-particle) shake-up bands in the valence ionization spectrum of odd-membered carbon rings (C5, C7, C9, C11) are investigated by means of the third-order algebraic diagrammatic construction [ADC(3)] scheme for the one-particle Green's function. Despite a severe dispersion of the σ- and π- ionization intensit...
The quartic force fields of FNO and CINO have been computed at the CCSD(T)/cc-pVTZ level. Using an "augmented" basis set dramatically improves results for FNO but has no significant effect for CINO. The best computed force field for FNO yields harmonic frequencies and fundamentals in excellent agreement with experiment. Overall, the force fields pr...
The ultraviolet (UV)–Visible absorption spectrum of trans-stilbene (tS) is computed at different temperatures by coupling molecular dynamics (MD) simulations with the classical MM3 force field to ZINDO/S-CIS calculations of vertical excitation energies and transition dipole moments. The selection of a large number of structures along the MD traject...
The vertical electron excitation spectra of linear carbon clusters C3, C5, and C7 have been investigated by means of polarization propagator calculations using the second-order algebraic diagrammatic construction [ADC(2)] scheme. The structure of singlet and triplet excited-state manifolds below the lowest ionization threshold has been analyzed in...
An extensive high-level computational study of various possible isomers of five, six and seven vertex closo-carboranes has been carried out using ab initio self-consistent field and density functional (DFT) theories. In total nine different cage structures have been investigated at the Hartree–Fock and B3LYP DFT levels in conjunction with the 6-31G...
The ground state geometry of trans-stilbene has been investigated using molecular mechanics, Hartree–Fock and density functional theories. The main goal of the present study is to evaluate the accuracy of the MM3 potential energy surfaces for this system. Overall, the MM3 force field provides geometries in reasonable agreement with those obtained a...
The intermolecular forces pertaining to the nucleation mechanism and the solid-state architecture of an eight-ring model oligomer of poly(p-phenylene vinylene) (PPV) have been investigated using molecular mechanics (MM3). An aggregate of PPV has been fully optimized at the MM3 level in order to characterize its packing conformation and crystallogra...
The article points out that the common sources of thermodynamic data do not respect optical isomerism though the substantial feature is not recognized. This fact implies widespread imprecisions involved in applications of the sources. The point is illustrated on difluorodisulfane. It is also pointed out that the chirality partition function plays a...
Owing to the three-fold degeneracy of the LUMO in C60, its hexa-anion is not subjected to Jahn-Teller distortions. In contrast to the accepted presumptions, however, computations at the MNDO, AMI, PM3, SAM1, HF/STO-3G, HF/3-21G, and HF/4-31G levels show that the completely relaxed, non-icosahedral cage of C 60is lower in energy. The computed energy...
The structural, rotational, and vibrational properties of BnNn+ clusters (n = 3−10) have been investigated using density functional theory (DFT) and compared with that of their neutral counterparts. The BnNn+ species with n = 4, 6, 8, 10 are found to possess as lowest energy form a fully regular structure of Dnh symmetry, as the neutral species. In...
The 1h (one-hole) and 2h-1p (two-hole; one-particle) shake-up bands in the valence ionization spectrum of small carbon rings (C4, C6, C8, C10) are investigated up to 40 eV, using the one-particle Green’s Function approach. Calculations have been performed using both the third-order algebraic diagrammatic construction [ADC(3)] scheme and the outer-v...
The ionization bands and electron affinities of medium-size BnNn clusters (n = 3, 4, 5) have been investigated by means of one-particle Green's function calculations using the outer-valence Green's function (OVGF) approximation or the third-order algebraic diagrammatic construction [ADC(3)] scheme. Despite their structural similarity with isoelectr...
The potential energy curves of the SiO(+) cation for the low-lying electronic states, correlating to the first two lowest dissociation channels (Si(+)((2)P(u)) + O((3)P(g)) and Si(+)((2)P(u)) + O((1)D(g))), have been calculated at the internally contracted multireference configuration interaction (CMRCI) level with Dunning's correlation-consistent...
The 1h (one-hole) and 2h-1p (two-hole; one-particle) shake-up bands in the valence ionization spectrum of small carbon chains (C3,C5,C7,C9) are investigated up to 40 eV, using the one-particle Green’s function approach. Calculations have been performed at the second- and third-orders of an algebraic diagrammatic construction (ADC) scheme based on p...
The structures, rotational moments, vibrational normal modes, and infrared spectra of small to medium-size ionized carbon clusters Cn+ (n = 4−19) are investigated using density functional (DFT) and coupled cluster (CC) theories. Comparison is made with the neutral systems from which they derive. In contrast to previous restricted open-shell Hartree...
A combination of the methods of Gardner and Prony is used for the qualitative and quantitative analysis of solid-state free induction decay (1H NMR) curves of isotactic polypropylene, recorded at 40, 60, 80, and 100 °C at constant time intervals. These multicomponent decay curves contain information about the physicochemical structure of the polyme...
The potential energy curves of the X2Σ+, A2Π, and B2Σ+ states of the SiC- anion and of the X3Π state of SiC have been calculated at the internally contracted multireference configuration interaction (CMRCI) level with Dunning's augmented correlation-consistent polarized valence quadruple-ζ (aug-cc-pVQZ) basis set. The equilibrium bond lengths (re),...
The equilibrium bond lengths, harmonic frequencies, first-order anharmonicity constants, rotational constants, centrifugal distortion constants, and rotation–vibrational constants, as well as the dipole moments, excitation and dissociation energies for the lowest , and states of SiN+ have been calculated using CASSCF, CMRCI, CCSD(T) and density fun...
Two complementary methods, the improved method of Gardner et al. and of Prony for the analysis of multicomponent decay curves, are presented. The improved method of Gardner et al. can be applied to determine the number of components and to estimate the decay constants. These can then be quantified together with the pre-exponential factors using the...