414 research outputs found
Evidence for Low-Dimensional Chaos in Semiregular Variable Stars
An analysis of the photometric observations of the light curves of the five
large amplitude, irregularly pulsating stars R UMi, RS Cyg, V CVn, UX Dra and
SX Her is presented. First, multi-periodicity is eliminated for these
pulsations, i.e. they are not caused by the excitation of a small number of
pulsation modes with constant amplitudes. Next, on the basis of energetics we
also eliminate stochasticity as a cause, leaving low dimensional chaos as the
only alternative. We then use a global flow reconstruction technique in an
attempt to extract quantitative information from the light curves, and to
uncover common physical features in this class of irregular variable stars that
straddle the RV Tau to the Mira variables. Evidence is presented that the
pulsational behavior of R UMi, RS Cyg, V CVn and UX Dra takes place in a
4-dimensional dynamical phase space, suggesting that two vibrational modes are
involved in the pulsation. A linear stability analysis of the fixed points of
the maps further indicates the existence of a two-mode resonance, similar to
the one we had uncovered earlier in R Sct: The irregular pulsations are the
result of a continual energy exchange between two strongly nonadiabatic modes,
a lower frequency pulsation mode and an overtone that are in a close 2:1
resonance. The evidence is particularly convincing for R UMi, RS Cyg and V CVn,
but much weaker for UX Dra. In contrast, the pulsations of SX Her appear to be
more complex and may require a 6D space.Comment: 20 pages, 14 figures, accepted in ApJ - paper with clearer figures is
available at http://www.phys.ufl.edu/~buchler/publications/u12.ps.gz (1Mb
Beyond Positive Scaling: How Negation Impacts Scaling Trends of Language Models
Language models have been shown to exhibit positive scaling, where
performance improves as models are scaled up in terms of size, compute, or
data. In this work, we introduce NeQA, a dataset consisting of questions with
negation in which language models do not exhibit straightforward positive
scaling. We show that this task can exhibit inverse scaling, U-shaped scaling,
or positive scaling, and the three scaling trends shift in this order as we use
more powerful prompting methods or model families. We hypothesize that solving
NeQA depends on two subtasks: question answering (task 1) and negation
understanding (task 2). We find that task 1 has linear scaling, while task 2
has sigmoid-shaped scaling with an emergent transition point, and composing
these two scaling trends yields the final scaling trend of NeQA. Our work
reveals and provides a way to analyze the complex scaling trends of language
models.Comment: Published at ACL 2023 Finding
Connect, Not Collapse: Explaining Contrastive Learning for Unsupervised Domain Adaptation
We consider unsupervised domain adaptation (UDA), where labeled data from a
source domain (e.g., photographs) and unlabeled data from a target domain
(e.g., sketches) are used to learn a classifier for the target domain.
Conventional UDA methods (e.g., domain adversarial training) learn
domain-invariant features to improve generalization to the target domain. In
this paper, we show that contrastive pre-training, which learns features on
unlabeled source and target data and then fine-tunes on labeled source data, is
competitive with strong UDA methods. However, we find that contrastive
pre-training does not learn domain-invariant features, diverging from
conventional UDA intuitions. We show theoretically that contrastive
pre-training can learn features that vary subtantially across domains but still
generalize to the target domain, by disentangling domain and class information.
Our results suggest that domain invariance is not necessary for UDA. We
empirically validate our theory on benchmark vision datasets.Comment: 35 page
Hypoxia Regulates BMP4 Expression in the Murine Spleen during the Recovery from Acute Anemia
Bone marrow erythropoiesis is primarily homeostatic, producing new erythrocytes at a constant rate. However at times of acute anemia, new erythrocytes must be rapidly produced much faster than bone marrow steady state erythropoiesis. At these times stress erythropoiesis predominates. Stress erythropoiesis occurs in the fetal liver during embryogenesis and in the adult spleen and liver. In adult mice, stress erythropoiesis utilizes a specialized population of stress erythroid progenitors that are resident in the spleen. In response to acute anemia, these progenitors rapidly expand and differentiate in response to three signals, BMP4, SCF and hypoxia. In absence of acute anemic stress, two of these signals, BMP4 and hypoxia, are not present and the pathway is not active. The initiating event in the activation of this pathway is the up-regulation of BMP4 expression in the spleen.In this paper we analyze the regulation of BMP4 expression in the spleen by hypoxia. Using stromal cell lines, we establish a role for hypoxia transcription factor HIFs (Hypoxia Inducible Factors) in the transcription of BMP4. We identified putative Hypoxia Responsive Elements (HREs) in the BMP4 gene using bioinformatics. Analysis of these elements showed that in vivo, Hif2alpha binds two cis regulatory sites in the BMP4 gene, which regulate BMP4 expression during the recovery from acute anemia.These data show that hypoxia plays a key role in initiating the BMP4 dependent stress erythropoiesis pathway by regulating BMP4 expression
Documentation for Emergency Stabilization and the Integrated Conservation Planning of Earthen Architecture Settlements: the Kasbah of Taourirt (Ouarzazate, Morocco)
Heritage recording serves as a basis for methodologies regarding diagnosis, treatment and preservation of historic places and contributes to make posterity records of our built cultural heritage. This work is not a stand-alone practice, but a part of the overall conservation of cultural heritage. Reco
Catalog of Galactic Beta Cephei Stars
We present an extensive and up-to-date catalog of Galactic Beta Cephei stars.
This catalog is intended to give a comprehensive overview of observational
characteristics of all known Beta Cephei stars. 93 stars could be confirmed to
be Beta Cephei stars. For some stars we re-analyzed published data or conducted
our own analyses. 61 stars were rejected from the final Beta Cephei list, and
77 stars are suspected to be Beta Cephei stars. A list of critically selected
pulsation frequencies for confirmed Beta Cephei stars is also presented. We
analyze the Beta Cephei stars as a group, such as the distributions of their
spectral types, projected rotational velocities, radial velocities, pulsation
periods, and Galactic coordinates. We confirm that the majority of these stars
are multiperiodic pulsators. We show that, besides two exceptions, the Beta
Cephei stars with high pulsation amplitudes are slow rotators. We construct a
theoretical HR diagram that suggests that almost all 93 Beta Cephei stars are
MS objects. We discuss the observational boundaries of Beta Cephei pulsation
and their physical parameters. We corroborate that the excited pulsation modes
are near to the radial fundamental mode in frequency and we show that the mass
distribution of the stars peaks at 12 solar masses. We point out that the
theoretical instability strip of the Beta Cephei stars is filled neither at the
cool nor at the hot end and attempt to explain this observation
Plan de negocios para la creaci?n de un call center de cobranzas enfocado en desarrollar una cultura organizacional que reduzca los altos ?ndices de rotaci?n maximizando los niveles de productividad
El presente trabajo tiene como objetivo crear una empresa de call center de cobranzas. A trav?s, de la investigaci?n te?rica y estudios cuantitativos se pudo validar la problem?tica de la rotaci?n y la cultura organizacional en los call center de cobranzas. As? tambi?n, a trav?s de estudios cualitativos como entrevistas, encuestas y focus group se pudo determinar o identificar los principales atributos y caracter?sticas que los clientes valoran al momento de contratar una empresa de call center. Se desarrollaron estrategias que pretende eliminar la brecha que existe entre lo que los clientes desean versus lo que el mercado ofrece. La estrategia de recursos humanos desarrolla una cultura organizacional de clan y mercado para retener al personal y elevar la productividad. La estrategia de marketing plantea un precio similar a la competencia, pero con un servicio diferenciado, por los altos niveles de productividad esperados. As? mismo, la estrategia operativa desarrollada permite identificar los procesos cr?ticos que deber?n ser monitoreados y auditados para evitar fallos que pudieran causar insatisfacci?n de los clientes. Con las estrategias definidas se eval?an los costos e ingresos mediante la evaluaci?n econ?mica que resulta con VAN positivo, que indica que el presente plan de negocios es viable
Peer-mentoring for first-time mothers from areas of socio-economic disadvantage: A qualitative study within a randomised controlled trial
<p>Abstract</p> <p>Background</p> <p>Non-professional involvement in delivering health and social care support in areas of socio-economic deprivation is considered important in attempting to reduce health inequalities. However, trials of peer mentoring programmes have yielded inconsistent evidence of benefit: difficulties in implementation have contributed to uncertainty regarding their efficacy. We aimed to explore difficulties encountered in conducting a randomised controlled trial of a peer-mentoring programme for first-time mothers in socially disadvantaged areas, in order to provide information relevant to future research and practice. This paper describes the experiences of lay-workers, women and health professionals involved in the trial.</p> <p>Methods</p> <p>Thematic analysis of semi-structured interviews with women (n = 11) who were offered peer mentor support, lay-workers (n = 11) who provided mentoring and midwives (n = 2) who supervised the programme, which provided support, from first hospital antenatal visit to one year postnatal. Planned frequency of contact was two-weekly (telephone or home visit) but was tailored to individuals' needs.</p> <p>Results</p> <p>Despite lay-workers living in the same locality, they experienced difficulty initiating contact with women and this affected their morale adversely. Despite researchers' attempts to ensure that the role of the mentor was understood clearly it appeared that this was not achieved for all participants. Mentors attempted to develop peer-mentor relationships by offering friendship and sharing personal experiences, which was appreciated by women. Mentors reported difficulties developing relationships with those who lacked interest in the programme. External influences, including family and friends, could prevent or facilitate mentoring. Time constraints in reconciling flexible mentoring arrangements with demands of other commitments posed major personal difficulties for lay-workers.</p> <p>Conclusion</p> <p>Difficulties in initiating contact, developing peer-mentor relationships and time constraints pose challenges to delivering lay-worker peer support. In developing such programmes, awareness of potential difficulties and of how professional support may help resolve these should improve uptake and optimise evaluation of their effectiveness.</p> <p>Trial Registration Number: ISRCTN55055030</p
Elentári: a massive proto-supercluster at z ∼ 3.3 in the COSMOS field
Motivated by spectroscopic confirmation of three overdense regions in the COSMOS field at z similar to 3.35, we analyse the uniquely deep multiwavelength photometry and extensive spectroscopy available in the field to identify any further related structure. We construct a three-dimensional density map using the Voronoi tesselation Monte Carlo method and find additional regions of significant overdensity. Here, we present and examine a set of six overdense structures at 3.20 < z < 3.45 in the COSMOS field, the most well-characterized of which, PCl J0959 + 0235, has 80 spectroscopically confirmed members and an estimated mass of 1.35 x 10(15) M-circle dot, and is modelled to virialize at z similar to 1.5-2.0. These structures contain 10 overdense peaks with >5 sigma overdensity separated by up to 70 cMpc, suggestive of a proto-supercluster similar to the Hyperion system at z similar to 2.45. Upcoming photometric surveys with JWST such as COSMOS-Web, and further spectroscopic follow-up will enable more extensive analysis of the evolutionary effects that such an environment may have on its component galaxies at these early times
Genome sequence of the cultivated cotton <i>Gossypium arboreum</i>
The complex allotetraploid nature of the cotton genome (AADD; 2n = 52) makes genetic, genomic and functional analyses extremely challenging. Here we sequenced and assembled the Gossypium arboreum (AA; 2n = 26) genome, a putative contributor of the A subgenome. A total of 193.6 Gb of clean sequence covering the genome by 112.6-fold was obtained by paired-end sequencing. We further anchored and oriented 90.4% of the assembly on 13 pseudochromosomes and found that 68.5% of the genome is occupied by repetitive DNA sequences. We predicted 41,330 protein-coding genes in G. arboreum. Two whole-genome duplications were shared by G. arboreum and Gossypium raimondii before speciation. Insertions of long terminal repeats in the past 5 million years are responsible for the twofold difference in the sizes of these genomes. Comparative transcriptome studies showed the key role of the nucleotide binding site (NBS)-encoding gene family in resistance to Verticillium dahliae and the involvement of ethylene in the development of cotton fiber cells.Genetics & HereditySCI(E)[email protected]; [email protected]; [email protected]
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