32,918 research outputs found
Sheffield University CLEF 2000 submission - bilingual track: German to English
We investigated dictionary based cross language information
retrieval using lexical triangulation. Lexical triangulation combines the results
of different transitive translations. Transitive translation uses a pivot language
to translate between two languages when no direct translation resource is
available. We took German queries and translated then via Spanish, or Dutch
into English. We compared the results of retrieval experiments using these
queries, with other versions created by combining the transitive translations or
created by direct translation. Direct dictionary translation of a query introduces
considerable ambiguity that damages retrieval, an average precision 79% below
monolingual in this research. Transitive translation introduces more ambiguity,
giving results worse than 88% below direct translation. We have shown that
lexical triangulation between two transitive translations can eliminate much of
the additional ambiguity introduced by transitive translation
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Steric and electronic control of an ultrafast isomerization.
Synthetic control of the influence of steric and electronic factors on the ultrafast (picosecond) isomerization of penta-coordinate ruthenium dithietene complexes (Ru((CF3)2C2S2)(CO)(L)2, where L = a monodentate phosphine ligand) is reported. Seven new ruthenium dithietene complexes were prepared and characterized by single crystal X-ray diffraction. The complexes are all square pyramidal and differ only in the axial vs. equatorial coordination of the carbonyl ligand. Fourier Transform Infrared (FTIR) spectroscopy was used to study the Ī½(CO) bandshapes of the complexes in solution, and these reveal rapid exchange between two or three isomers of each complex. Isomerization is proposed to follow a Berry psuedorotation-like mechanism where a metastable, trigonal bipyramidal (TBP) intermediate is observed spectroscopically. Electronic tuning of the phosphine ligands L = PPh3, P((p-Me)Ph)3, ((p-Cl)Ph)3, at constant cone angle is found to have little effect on the kinetics or thermodynamic stabilities of the axial, equatorial and TBP isomers of the differently substituted complexes. Steric tuning of the phosphine ligands over a range of phosphine cone angles (135 < Īø < 165Ā°) has a profound impact on the isomerization process, and in the limit of greatest steric bulk, the axial isomer is not observable. Temperature dependence of the FTIR spectra was used to obtain the relative thermodynamic stabilities of the different isomers of each of the seven ruthenium dithietene complexes. This study details how ligand steric effects can be used to direct the solution state dynamics on the picosecond time scale of discrete isomers energetically separated by <2.2 kcal mol-1. This work provides the most detailed description to date of ultrafast isomerization in the ground states of transition metal complexes
Restrictions and Stability of Time-Delayed Dynamical Networks
This paper deals with the global stability of time-delayed dynamical
networks. We show that for a time-delayed dynamical network with
non-distributed delays the network and the corresponding non-delayed network
are both either globally stable or unstable. We demonstrate that this may not
be the case if the network's delays are distributed. The main tool in our
analysis is a new procedure of dynamical network restrictions. This procedure
is useful in that it allows for improved estimates of a dynamical network's
global stability. Moreover, it is a computationally simpler and much more
effective means of analyzing the stability of dynamical networks than the
procedure of isospectral network expansions introduced in [Isospectral graph
transformations, spectral equivalence, and global stability of dynamical
networks. Nonlinearity, 25 (2012) 211-254]. The effectiveness of our approach
is illustrated by applications to various classes of Cohen-Grossberg neural
networks.Comment: 32 pages, 9 figure
The Impact of Cultural Familiarity on Studentsā Social Media Usage in Higher Education
Using social media (SM) in Higher education (HE) becomes unavoidable in the new teaching and learning pedagogy.
The current generation of students creates their groups on SM for collaboration. However, SM can be a primary source of
learning distraction due to its nature, which does not support structured learning. Hence, derived from the literature, this study proposes three learning customised system features, to be implemented on SM when used in Higher Education HE.
Nevertheless, some psychological factors appear to have a stronger impact on studentsā adoption of SM in learning than the proposed features. A Quantitative survey was conducted at a university in Uzbekistan to collect 52 undergraduate studentsā perception of proposed SM learning customised features in Moodle. These features aim to provide localised, personalised, and privacy control self-management environment for collaboration in Moodle. These features could be significant in predicting studentsā engagement with SM in HE. The data analysis showed a majority of positive feedback towards the proposed learning customised SM. However, the surveyed studentsā engagement with these features was observed as minimal. The course leader initiated a semi-structured interview to investigate the reason. Although the students confirmed their acceptance of the learning customised features, their preferences to alternate SM, which is Telegram overridden their usage of the proposed learning customized SM, which is Twitter. The students avoided the Moodle integrated Twitter (which provided highly accepted features) and chose to use the Telegram as an external collaboration platform driven by their familiarity and social preferences with the Telegram since it is the popular SM in Uzbekistan. This study is part of an ongoing PhD research which involves deeper frame of learnersā cognitive usage of the learning management system. However, this paper exclusively discusses the cultural familiarity impact of studentās adoption of SM in HE
Finite-difference distributions for the Ginibre ensemble
The Ginibre ensemble of complex random matrices is studied. The complex
valued random variable of second difference of complex energy levels is
defined. For the N=3 dimensional ensemble are calculated distributions of
second difference, of real and imaginary parts of second difference, as well as
of its radius and of its argument (angle). For the generic N-dimensional
Ginibre ensemble an exact analytical formula for second difference's
distribution is derived. The comparison with real valued random variable of
second difference of adjacent real valued energy levels for Gaussian
orthogonal, unitary, and symplectic, ensemble of random matrices as well as for
Poisson ensemble is provided.Comment: 8 pages, a number of small changes in the tex
Severity of disease and risk of malignant change in hereditary multiple exostoses. A genotype-phenotype study
We performed a prospective genotype-phenotype study using molecular screening and clinical assessment to compare the severity of disease and the risk of sarcoma in 172 individuals (78 families) with hereditary multiple exostoses. We calculated the severity of disease including stature, number of exostoses, number of surgical procedures that were necessary, deformity and functional parameters and used molecular techniques to identify the genetic mutations in affected individuals. Each arm of the genotype-phenotype study was blind to the outcome of the other. Mutations EXT1 and EXT2 were almost equally common, and were identified in 83% of individuals. Non-parametric statistical tests were used. There was a wide variation in the severity of disease. Children under ten years of age had fewer exostoses, consistent with the known age-related penetrance of this condition. The severity of the disease did not differ significantly with gender and was very variable within any given family. The sites of mutation affected the severity of disease with patients with EXT1 mutations having a significantly worse condition than those with EXT2 mutations in three of five parameters of severity (stature, deformity and functional parameters). A single sarcoma developed in an EXT2 mutation carrier, compared with seven in EXT1 mutation carriers. There was no evidence that sarcomas arose more commonly in families in whom the disease was more severe. The sarcoma risk in EXT1 carriers is similar to the risk of breast cancer in an older population subjected to breast-screening, suggesting that a role for regular screening in patients with hereditary multiple exostoses is justifiable. Ā©2004 British Editorial Society of Bone and Joint Surgery
Observation of discrete energy levels in a quantum confined system
Low temperature scanning tunneling microscope images and spectroscopic data
have been obtained on subnanometer size Pb clusters fabricated using the
technique of buffer layer assisted growth. Discrete energy levels were resolved
in current-voltage characteristics as current peaks rather than current steps.
Distributions of peak voltage spacings and peak current heights were consistent
with Wigner-Dyson and Porter-Thomas distributions respectively, suggesting the
relevance of random matrix theory to the description of the electronic
eigenstates of the clusters. The observation of peaks rather than steps in the
current-voltage characteristics is attributed to a resonant tunneling process
involving the discrete energy levels of the cluster, the tip, and the states at
the interface between the cluster and the substrate surface.Comment: 4 pages, 4 figure
Lighting as a Circadian Rhythm-Entraining and Alertness-Enhancing Stimulus in the Submarine Environment
The human brain can only accommodate a circadian rhythm that closely follows 24 hours. Thus, for a work schedule to meet the brainās hard-wired requirement, it must employ a 24 hour-based program. However, the 6 hours on, 12 hours off (6/12) submarine watchstanding schedule creates an 18-hour ādayā that Submariners must follow. Clearly, the 6/12 schedule categorically fails to meet the brainās operational design, and no schedule other than one tuned to the brainās 24 hour rhythm can optimize performance. Providing Submariners with a 24 hour-based watchstanding scheduleācombined with effective circadian entrainment techniques using carefully-timed exposure to lightāwould allow crewmembers to work at the peak of their daily performance cycle and acquire more restorative sleep. In the submarine environment, where access to natural light is absent, electric lighting can play an important role in actively entrainingāand closely maintainingācircadian regulation. Another area that is likely to have particular importance in the submarine environment is the potential effect of light to help restore or maintain alertness
Improved He I Emissivities in the Case B Approximation
We update our prior work on the case B collisional-recombination spectrum of
He I to incorporate \textit{ab initio} photoionisation cross-sections. This
large set of accurate, self-consistent cross-sections represents a significant
improvement in He I emissivity calculations because it largely obviates the
piecemeal nature that has marked all modern works. A second, more recent set of
\textit{ab initio} cross-sections is also available, but we show that those are
less consistent with bound-bound transition probabilities than our adopted set.
We compare our new effective recombination coefficients with our prior work and
our new emissivities with those by other researchers, and we conclude with
brief remarks on the effects of the present work on the He I error budget. Our
calculations cover temperatures K and densities cm. Full results are available online.Comment: Accepted to MNRAS Letters; 4 pages, 4 figures, 2 tables, 1
supplemental fil
Signatures of Random Matrix Theory in the Discrete Energy Spectra of Subnanosize Metallic Clusters
Lead clusters deposited on Si(111) substrates have been studied at low
temperatures using scanning tunneling microscopy and spectroscopy. The
current-voltage characteristics exhibit current peaks that are irregularly
spaced and varied in height. The statistics of the distribution of peak heights
and spacings are in agreement with random matrix theory for several clusters.
The distributions have also been studied as a function of cluster shape.Comment: 10 pages, 9 figures, to appear in Phys. Rev.
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