1,259 research outputs found
Symmetry adapted ro-vibrational basis functions for variational nuclear motion calculations: TROVE approach
We present a general, numerically motivated approach to the construction of
symmetry adapted basis functions for solving ro-vibrational Schr\"{o}dinger
equations. The approach is based on the property of the Hamiltonian operator to
commute with the complete set of symmetry operators and hence to reflect the
symmetry of the system. The symmetry adapted ro-vibrational basis set is
constructed numerically by solving a set of reduced vibrational eigenvalue
problems. In order to assign the irreducible representations associated with
these eigenfunctions, their symmetry properties are probed on a grid of
molecular geometries with the corresponding symmetry operations. The
transformation matrices are re-constructed by solving over-determined systems
of linear equations related to the transformation properties of the
corresponding wavefunctions on the grid. Our method is implemented in the
variational approach TROVE and has been successfully applied to a number of
problems covering the most important molecular symmetry groups. Several
examples are used to illustrate the procedure, which can be easily applied to
different types of coordinates, basis sets, and molecular systems
Correction of artificial jumps in the historical geomagnetic measurements of Coimbra Observatory, Portugal
The Coimbra Magnetic Observatory (International Association of Geomagnetism and Aeronomy code COI) in Portugal has a long
history of observation of the geomagnetic field, spanning almost 150 yr
since the first geomagnetic measurements in 1866. These long instrumental
geomagnetic records provide very important information about variability of
geomagnetic elements and indices, their trends and cycles, and can be used
to improve our knowledge on the sources that drive variations of the
geomagnetic field: liquid core dynamics (internal) and solar forcing
(external).
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However, during the long life of the Coimbra Observatory, some inevitable
changes in station location, instrument's park and electromagnetic
environment have taken place. These changes affected the quality of the data
collected at COI causing breaks and jumps in the series of geomagnetic field
components and local K index. Clearly, these inhomogeneities, typically
shift-like (step-like) or trend-like, have to be corrected or, at least,
minimized in order for the data to be used in scientific studies or to be
submitted to international databases.
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In this study, the series of local K index and declination of the
geomagnetic field are analysed: the former because it allows direct
application of standard homogenization methods and the latter because it is
the longest continuous series produced at COI. For the homogenization,
visual and statistical tests (e.g. standard normal homogeneity test) have
been applied directly to the local geomagnetic K index series (from 1951 to
2012). The homogenization of the monthly averages of declination (from 1867
to 2012) has been done using visual analysis and statistical tests applied
to the time series of the first differences of declination values, as an
approximation to the first time derivative. This allowed not only
estimating the level of inhomogeneity of the studied series but also
detecting the highly probable homogeneity break points. These points have been
cross-checked with the metadata, and the COI series have been compared with
reference series from the nearest geomagnetic stations and, in the case of
declination series, from the recent geomagnetic field model COV-OBS to set
up the required correction factors. As a result, the homogenized series
measured in COI are considered to be essentially free of artificial shifts
starting from the second half of the 20th century, and ready to be used by
the scientific community
Effect of carbamylated darbepoetin administration at different doses on the thymus and spleen structure of rats
In this article, the morphological features of the structure of the thymus and spleen under the influence of carbamylated darbepoetin in different doses were studied. The material for the study was 40 white male rats of the Wistar bree
Volume of the quantum mechanical state space
The volume of the quantum mechanical state space over -dimensional real,
complex and quaternionic Hilbert-spaces with respect to the canonical Euclidean
measure is computed, and explicit formulas are presented for the expected value
of the determinant in the general setting too. The case when the state space is
endowed with a monotone metric or a pull-back metric is considered too, we give
formulas to compute the volume of the state space with respect to the given
Riemannian metric. We present the volume of the space of qubits with respect to
various monotone metrics. It turns out that the volume of the space of qubits
can be infinite too. We characterize those monotone metrics which generates
infinite volume.Comment: 17 page
Results of hydrological studies and channel analysis of the Ganges (Padma) River at the construction site of the “Rooppur” NPP
This work presents the results of research on channel processes in the Padma River (Republic of Bangladesh) at the construction site of the “Ruppur” Nuclear Power Plant (NPP). The fluvial characteristics of the Padma River were presented, including: the water outflow regime, characteristics of anthropogenic impact on the river outflow and assessment of the present state of the channel and floodplain. The research was conducted based on field expeditions, during which data on morphology, dynamics, hydrological and hydraulic conditions for the formation of the floodplain-channel complex were collected. Moreover, the water discharges and suspended sediments, as well as the longitudinal profiles of the water level and the channel morphology were measured. The presented research has shown that comprehensive and planned regulation of selected sections of rivers could lead to the channel stabilization and support the rational use of water resources for different purposes, e.g. power plants, municipal purposes, etc. Moreover, detailed research on channel deformation in selected areas indicated the major role of natural factors (geological structure, the type of sediments delivered to the river, vegetation cover, etc.) in the past and present fluvial processes
Observation of the Early Structural Changes Leading to the Formation of Protein Superstructures.
Formation of superstructures in protein aggregation processes has been indicated as a general pathway for several proteins, possibly playing a role in human pathologies. There is a severe lack of knowledge on the origin of such species in terms of both mechanisms of formation and structural features. We use equine lysozyme as a model protein, and by combining spectroscopic techniques and microscopy with X-ray fiber diffraction and ab initio modeling of Small Angle X-ray Scattering data, we isolate the partially unfolded state from which one of these superstructures (i.e., particulate) originates. We reveal the low-resolution structure of the unfolded state and its mechanism of formation, highlighting the physicochemical features and the possible pathway of formation of the particulate structure. Our findings provide a novel detailed knowledge of such a general and alternative aggregation pathway for proteins, this being crucial for a basic and broader understanding of the aggregation phenomena.This is the author's accepted manuscript and will be under embargo until the 3rd of September 2015. The final version is published by ACS in The Journal of Physical Chemistry Letters here: http://pubs.acs.org/doi/abs/10.1021/jz501614e
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