37 research outputs found
The Raman spectrum of CaCO3 polymorphs calcite and aragonite: A combined experimental and computational study
Powder and single crystal Raman spectra of the two most common phases of calcium carbonate are calculated with ab initio techniques (using a “hybrid” functional and a Gaussian-type basis set) and measured both at 80 K and room temperature. Frequencies of the Raman modes are in very good agreement between calculations and experiments: the mean absolute deviation at 80 K is 4 and 8 cm−1 for calcite and aragonite, respectively. As regards intensities, the agreement is in general good, although the computed values overestimate the measured ones in many cases. The combined analysis permits to identify almost all the fundamental experimental Raman peaks of the two compounds, with the exception of either modes with zero computed intensity or modes overlapping with more intense peaks. Additional peaks have been identified in both calcite and aragonite, which have been assigned to 18O satellite modes or overtones. The agreement between the computed and measured spectra is quite satisfactory; in particular, simulation permits to clearly distinguish between calcite and aragonite in the case of powder spectra, and among different polarization directions of each compound in the case of single crystal spectra
The vibrational spectrum of CaCO3 aragonite: A combined experimental and quantum-mechanical investigation
The vibrational properties of CaCO3 aragonite have been investigated both theoretically, by using a quantum mechanical approach (all electron Gaussian type basis set and B3LYP HF-DFT hybrid functional, as implemented in the CRYSTAL code) and experimentally, by collecting polarized infrared (IR) reflectance and Raman spectra. The combined use of theory and experiment permits on the one hand to analyze the many subtle features of the measured spectra, on the other hand to evidentiate limits and deficiencies of both approaches. The full set of TO and LO IR active modes, their intensities, the dielectric tensor (in its static and high frequency components), and the optical indices have been determined, as well as the Raman frequencies. Tools such as isotopic substitution and graphical animation of the modes are available, that complement the analysis of the spectrum
Generalised quantum weakest preconditions
Generalisation of the quantum weakest precondition result of D'Hondt and
Panangaden is presented. In particular the most general notion of quantum
predicate as positive operator valued measure (POVM) is introduced. The
previously known quantum weakest precondition result has been extended to cover
the case of POVM playing the role of a quantum predicate. Additionally, our
result is valid in infinite dimension case and also holds for a quantum
programs defined as a positive but not necessary completely positive
transformations of a quantum states.Comment: 7 pages, no figures, added references, changed conten
Quantum walks: a comprehensive review
Quantum walks, the quantum mechanical counterpart of classical random walks,
is an advanced tool for building quantum algorithms that has been recently
shown to constitute a universal model of quantum computation. Quantum walks is
now a solid field of research of quantum computation full of exciting open
problems for physicists, computer scientists, mathematicians and engineers.
In this paper we review theoretical advances on the foundations of both
discrete- and continuous-time quantum walks, together with the role that
randomness plays in quantum walks, the connections between the mathematical
models of coined discrete quantum walks and continuous quantum walks, the
quantumness of quantum walks, a summary of papers published on discrete quantum
walks and entanglement as well as a succinct review of experimental proposals
and realizations of discrete-time quantum walks. Furthermore, we have reviewed
several algorithms based on both discrete- and continuous-time quantum walks as
well as a most important result: the computational universality of both
continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing
Journa
Percutaneous internal fixation with Y-STRUT® device to prevent both osteoporotic and pathological hip fractures: a prospective pilot study
The Lacemakers: Remembering Women's Lives
In this thesis I explored stories women told about their own lives and identified themes related to dominant discourses that were threaded in the stories. I looked at the linked sites of social reproduction, the family and social class, as analytical frameworks of gender construction, through the lens of feminist poststructural theory. Data was obtained using collective biography and a storytelling method was also used to present findings. Taking the view that the researcher is inextricably embedded in the research I have included autobiographical stories about experiences that impacted on this work, motivated my approach or were responses to the participants' experiences and stories. This autobiographical material is found in journal, story, poetry and theoretical writing
Cortinarius subgenus Leprocybe in Europe: expanded Sanger and Next Generation Sequencing unveil unexpected diversity in the Mediterranean
Molecular phylogenies in the past decade have demonstrated that the described diversity of Cortinarius
is still underestimated, especially outside continental and boreal ecoregions where the genus has been historically investigated. We tackled this issue by revisiting the so far unresolved subgenus Leprocybe, and focused on
the largely unexplored Mediterranean hotspot of biodiversity. The sequencing and phylogenetic analysis of 161
vouchered collections from Austria, Cyprus, France, Germany, Italy and Spain, including 16 types, allowed for the
delineation of 11 species in this lineage, three of them recognised as new to science and formally introduced as
C. jimenezianus, C. selinolens and C. viridans spp. nov., respectively. Interestingly, the newly described species
exhibit a strict Mediterranean distribution, and one of them is putatively endemic to the island of Cyprus, highlighting
the remarkable potential of this neglected ecoregion to uncover further undescribed diversity of Cortinarius in the
future. The present work also unveils 23 synonymies in this subgenus, as well as previously undetected crypticism
within C. venetus. Next Generation Sequencing carried out on three old and contaminated holotypes, successfully
decrypts their phylogenetic identity, including that of C. leproleptopus, finally settling the long-standing controversy
over the taxonomic status of this species. A brief overview of each species in the subgenus is lastly provided and a
key is proposed to facilitate the identification of presently known European taxa of Leprocybe in the field