Magnetic properties of single-crystalline CeCuGa3

The magnetic behavior of single-crystalline CeCuGa3 has been investigated. The compound forms in a tetragonal BaAl4-type structure consisting of rare-earth planes separated by Cu-Ga layers. If the Cu-Ga site disorder is reduced, CeCuGa3 adopts the related, likewise tetragonal BaNiSn3-type structure, in which the Ce ion are surrounded by different Cu and Ga layers and the inversion symmetry is lost. In the literature conflicting reports about the magnetic order of CeCuGa3 have been published. Single crystals with the centrosymmetric structure variant exhibit ferromagnetic order below approx. 4 K with a strong planar anisotropy. The magnetic behavior above the transition temperature can be well understood by the crystal-field splitting of the 4f Hund's rule ground-state multiplet of the Ce ions

Doping dependence of the carrier lifetime crossover point upon dissociation of iron-boron pairs in crystalline silicon

The excess carrier density at which the carrier lifetime in crystalline silicon remains unchanged after dissociating iron-boron pairs, known as the crossover point, is reported as a function of the borondopant concentration. Modeling this doping dependence with the Shockley-Read-Hall model does not require knowledge of the iron concentration and suggests a possible refinement of reported values of the capture cross sections for electrons and holes of the acceptor level of iron-boron pairs. In addition, photoluminescence-based measurements were found to offer some distinct advantages over traditional photoconductance-based techniques in determining recombination parameters from low-injection carrier lifetimes.This work has been supported by the Australian Research Council

Hartree-Fock and Many-Body Perturbation Theory with Correlated Realistic NN-Interactions

We employ correlated realistic nucleon-nucleon interactions for the description of nuclear ground states throughout the nuclear chart within the Hartree-Fock approximation. The crucial short-range central and tensor correlations, which are induced by the realistic interaction and cannot be described by the Hartree-Fock many-body state itself, are included explicitly by a state-independent unitary transformation in the framework of the unitary correlation operator method (UCOM). Using the correlated realistic interaction V_UCOM resulting from the Argonne V18 potential, bound nuclei are obtained already on the Hartree-Fock level. However, the binding energies are smaller than the experimental values because long-range correlations have not been accounted for. Their inclusion by means of many-body perturbation theory leads to a remarkable agreement with experimental binding energies over the whole mass range from He-4 to Pb-208, even far off the valley of stability. The observed perturbative character of the residual long-range correlations and the apparently small net effect of three-body forces provides promising perspectives for a unified nuclear structure description.Comment: 14 pages, 8 figures, 3 tables, using REVTEX

Associations between diurnal preference, sleep quality and externalizing behaviours: a behavioural genetic analysis

Background - Certain aspects of sleep co-occur with externalizing behaviours in youth, yet little is known about these associations in adults. The present study: (1) examines the associations between diurnal preference (morningness versus eveningness), sleep quality and externalizing behaviours; (2) explores the extent to which genetic and environmental influences are shared between or are unique to these phenotypes; (3) examines the extent to which genetic and environmental influences account for these associations. Method - Questionnaires assessing diurnal preference, sleep quality and externalizing behaviours were completed by 1556 young adult twins and siblings. Results - A preference for eveningness and poor sleep quality were associated with greater externalizing symptoms [r=0.28 (95% CI 0.23–0.33) and 0.34 (95% CI 0.28–0.39), respectively]. A total of 18% of the genetic influences on externalizing behaviours were shared with diurnal preference and sleep quality and an additional 14% were shared with sleep quality alone. Non-shared environmental influences common to the phenotypes were small (2%). The association between diurnal preference and externalizing behaviours was mostly explained by genetic influences [additive genetic influence (A)=80% (95% CI 0.56–1.01)], as was the association between sleep quality and externalizing behaviours [A=81% (95% CI 0.62–0.99)]. Non-shared environmental (E) influences accounted for the remaining variance for both associations [E=20% (95% CI −0.01 to 0.44) and 19% (95% CI 0.01–0.38), respectively]. Conclusions - A preference for eveningness and poor sleep quality are moderately associated with externalizing behaviours in young adults. There is a moderate amount of shared genetic influences between the phenotypes and genetic influences account for a large proportion of the association between sleep and externalizing behaviours. Further research could focus on identifying specific genetic polymorphisms common to both sleep and externalizing behaviours

Magnetic-field induced resistivity minimum with in-plane linear magnetoresistance of the Fermi liquid in SrTiO3-x single crystals

We report novel magnetotransport properties of the low temperature Fermi liquid in SrTiO3-x single crystals. The classical limit dominates the magnetotransport properties for a magnetic field perpendicular to the sample surface and consequently a magnetic-field induced resistivity minimum emerges. While for the field applied in plane and normal to the current, the linear magnetoresistance (MR) starting from small fields (< 0.5 T) appears. The large anisotropy in the transverse MRs reveals the strong surface interlayer scattering due to the large gradient of oxygen vacancy concentration from the surface to the interior of SrTiO3-x single crystals. Moreover, the linear MR in our case was likely due to the inhomogeneity of oxygen vacancies and oxygen vacancy clusters, which could provide experimental evidences for the unusual quantum linear MR proposed by Abrikosov [A. A. Abrikosov, Phys. Rev. B 58, 2788 (1998)].Comment: 5 pages, 4 figure

Momentum dependence of orbital excitations in Mott-insulating titanates

High-resolution resonant inelastic x-ray scattering has been used to determine the momentum dependence of orbital excitations in Mott-insulating LaTiO$_3$ and YTiO$_3$ over a wide range of the Brillouin zone. The data are compared to calculations in the framework of lattice-driven and superexchange-driven orbital ordering models. A superexchange model in which the experimentally observed modes are attributed to two-orbiton excitations yields the best description of the data.Comment: to appear in PR

Indirect RKKY interaction in any dimensionality

We present an analytical method which enables one to find the exact spatial dependence of the indirect RKKY interaction between the localized moments via the conduction electrons for the arbitrary dimensionality $n$. The corresponding momentum dependence of the Lindhard function is exactly found for any $n$ as well. Demonstrating the capability of the method we find the RKKY interaction in a system of metallic layers weakly hybridized to each other. Along with usual $2k_F$ in-plane oscillations the RKKY interaction has the sign-reversal character in a direction perpendicular to layers, thus favoring the antiferromagnetic type of layers' stacking.Comment: 3 pages, REVTEX, accepted to Phys.Rev.

Generating Abstractive Summaries from Meeting Transcripts

Summaries of meetings are very important as they convey the essential content of discussions in a concise form. Generally, it is time consuming to read and understand the whole documents. Therefore, summaries play an important role as the readers are interested in only the important context of discussions. In this work, we address the task of meeting document summarization. Automatic summarization systems on meeting conversations developed so far have been primarily extractive, resulting in unacceptable summaries that are hard to read. The extracted utterances contain disfluencies that affect the quality of the extractive summaries. To make summaries much more readable, we propose an approach to generating abstractive summaries by fusing important content from several utterances. We first separate meeting transcripts into various topic segments, and then identify the important utterances in each segment using a supervised learning approach. The important utterances are then combined together to generate a one-sentence summary. In the text generation step, the dependency parses of the utterances in each segment are combined together to create a directed graph. The most informative and well-formed sub-graph obtained by integer linear programming (ILP) is selected to generate a one-sentence summary for each topic segment. The ILP formulation reduces disfluencies by leveraging grammatical relations that are more prominent in non-conversational style of text, and therefore generates summaries that is comparable to human-written abstractive summaries. Experimental results show that our method can generate more informative summaries than the baselines. In addition, readability assessments by human judges as well as log-likelihood estimates obtained from the dependency parser show that our generated summaries are significantly readable and well-formed.Comment: 10 pages, Proceedings of the 2015 ACM Symposium on Document Engineering, DocEng' 201

The effect of alcohol on cervical and ocular vestibular evoked myogenic potentials in healthy volunteers

OBJECTIVE: We investigated the effect of alcohol on the cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs). As alcohol produces gaze-evoked nystagmus (GEN), we also tested the effect of nystagmus independent of alcohol by recording oVEMPs during optokinetic stimulation (OKS). METHODS: The effect of alcohol was tested in 14 subjects over multiple rounds of alcohol consumption up to a maximum breath alcohol concentration (BrAC) of 1.5‰ (mean 0.97‰). The effect of OKS was tested in 11 subjects at 5, 10 and 15deg/sec. RESULTS: oVEMP amplitude decreased from baseline to the highest BrAC level by 27% (range 5-50%, P<0.001), but there was no significant effect on oVEMP latency or cVEMP amplitude or latency. There was a significant negative effect of OKS on oVEMP amplitude (16%, P=0.006). CONCLUSIONS: We found a selective effect of alcohol on oVEMP amplitude, but no effect on the cVEMP. Vertical nystagmus elicited by OKS reduced oVEMP amplitude. SIGNIFICANCE: Alcohol selectively affects oVEMP amplitude. Despite the effects of alcohol and nystagmus, both reflexes were reliably recorded in all subjects and conditions. An absent response in a patient affected by alcohol or nystagmus indicates a vestibular deficit

Bounds for graph regularity and removal lemmas

We show, for any positive integer k, that there exists a graph in which any equitable partition of its vertices into k parts has at least ck^2/\log^* k pairs of parts which are not \epsilon-regular, where c,\epsilon>0 are absolute constants. This bound is tight up to the constant c and addresses a question of Gowers on the number of irregular pairs in Szemer\'edi's regularity lemma. In order to gain some control over irregular pairs, another regularity lemma, known as the strong regularity lemma, was developed by Alon, Fischer, Krivelevich, and Szegedy. For this lemma, we prove a lower bound of wowzer-type, which is one level higher in the Ackermann hierarchy than the tower function, on the number of parts in the strong regularity lemma, essentially matching the upper bound. On the other hand, for the induced graph removal lemma, the standard application of the strong regularity lemma, we find a different proof which yields a tower-type bound. We also discuss bounds on several related regularity lemmas, including the weak regularity lemma of Frieze and Kannan and the recently established regular approximation theorem. In particular, we show that a weak partition with approximation parameter \epsilon may require as many as 2^{\Omega(\epsilon^{-2})} parts. This is tight up to the implied constant and solves a problem studied by Lov\'asz and Szegedy.Comment: 62 page