1,241 research outputs found
Observations on the distinctive cream-coloured leaves of Combretum nelsonii Dümmer
The ultrastructure of the cream-coloured leaves subtending the flowers and of the leaves of Combretum nelsonii, is described. The cream leaves, which are shed as the fruits mature, lack functional plastids within the irregularly-shaped palisade, although the spongy mesophyll cells are photosynthetically active. Abundant air-spaces below the papillate upper epidermis and between the palisade cells cause light to be refracted within the cream leaves, contributing to their pale colour. Cream leaves do not regreen but become obscured by younger green leaves
Amplification of SOX4 promotes PI3K/Akt signaling in human breast cancer
Purpose: The PI3K/Akt signaling axis contributes to the dysregulation of many dominant features in breast cancer including cell proliferation, survival, metabolism, motility, and genomic instability. While multiple studies have demonstrated that basal-like or triple-negative breast tumors have uniformly high PI3K/Akt activity, genomic alterations that mediate dysregulation of this pathway in this subset of highly aggressive breast tumors remain to be determined. Methods: In this study, we present an integrated genomic analysis based on the use of a PI3K gene expression signature as a framework to analyze orthogonal genomic data from human breast tumors, including RNA expression, DNA copy number alterations, and protein expression. In combination with data from a genome-wide RNA-mediated interference screen in human breast cancer cell lines, we identified essential genetic drivers of PI3K/Akt signaling. Results: Our in silico analyses identified SOX4 amplification as a novel modulator of PI3K/Akt signaling in breast cancers and in vitro studies confirmed its role in regulating Akt phosphorylation. Conclusions: Taken together, these data establish a role for SOX4-mediated PI3K/Akt signaling in breast cancer and suggest that SOX4 may represent a novel therapeutic target and/or biomarker for current PI3K family therapies
The magnetic field topology associated to two M flares
On 27 October, 2003, two GOES M-class flares occurred in the lapse of three
hours in active region NOAA 10486. The two flares were confined and their
associated brightenings appeared at the same location, displaying a very
similar shape both at the chromospheric and coronal levels. We focus on the
analysis of magnetic field (SOHO/MDI), chromospheric (HASTA, Kanzelhoehe Solar
Observatory, TRACE) and coronal (TRACE) observations. By combining our data
analysis with a model of the coronal magnetic field, we compute the magnetic
field topology associated to the two M flares. We find that both events can be
explained in terms of a localized magnetic reconnection process occurring at a
coronal magnetic null point. This null point is also present at the same
location one day later, on 28 October, 2003. Magnetic energy release at this
null point was proposed as the origin of a localized event that occurred
independently with a large X17 flare on 28 October, 2003, at 11:01 UT. The
three events, those on 27 October and the one on 28 October, are homologous.
Our results show that coronal null points can be stable topological structures
where energy release via magnetic reconnection can happen, as proposed by
classical magnetic reconnection models.Comment: 14 pages, 7 figure
Fools gold? Developer dilemmas in a closed mobile application market platform
In this paper, we outline some potential conflicts that platform owners and
software developers face in mobile application markets. Our arguments are based
on comments captured in specialized online discussion forums, in which
developers gather to share knowledge and experiences. The key findings indicate
conflicts of interests, including 1) intra-platform competition, 2)
discriminative promotion, 3) entry prevention, 4) restricted monetization, 5)
restricted knowledge sharing, 6) substitution, and 7) strategic technology
selection. Opportunistic platform owners may use their power to discriminate
between third-part software developers. However, there are also potential
strategic solutions that developers can apply; for example diversification
(multi-homing), syndication and brand building.Comment: Presented at the 15th International Conference on Electronic
Commerce, ICEC 2013, Turku, Finland, August 13-15, 201
Insulin-like growth factor-1 receptor inhibitor, AMG-479, in cetuximab-refractory head and neck squamous cell carcinoma
Background Recurrent head and neck squamous cell carcinoma (HNSCC) remains a difficult cancer to treat. Here, we describe a patient with HNSCC who had complete response to methotrexate (MTX) after progressing on multiple cytotoxic agents, cetuximab, and AMG-479 (monoclonal antibody against insulin-like growth factor-1 receptor [IGF-1R]). Methods The clinical information was collected by a retrospective medical record review under an Institutional Review Board-approved protocol. From 4 tumors and 2 normal mucosal epithelia, global gene expression, and IGF-1R and dihydrofolate reductase (DHFR) protein levels were determined. Results Effective target inhibition in the tumor was confirmed by the decreased protein levels of total and phospho-IGF-1R after treatment with AMG-479. Decreased level of DHFR and conversion of a gene expression profile associated with cetuximab-resistance to cetuximab-sensitivity were also observed. Conclusion This suggests that the combination of AMG-479 and MTX or cetuximab may be a promising therapeutic approach in refractory HNSCC
Star formation and environmental quenching of GEEC2 group galaxies at z ∼ 1
We present new analysis from the Group Environment Evolution Collaboration 2 (GEEC2) spectroscopic survey of galaxy groups at 0.8 < z < 1. Our previous work revealed an intermediate population between the star-forming and quiescent sequences and a strong environmental dependence in the fraction of quiescent galaxies. Only ∼5 per cent of star-forming galaxies in both the group and field sample show a significant enhancement in star formation, which suggests that quenching is the primary process in the transition from the star-forming to the quiescent state. To model the environmental quenching scenario, we have tested the use of different exponential quenching time-scales and delays between satellite accretion and the onset of quenching. We find that with no delay, the quenching time-scale needs to be long in order to match the observed quiescent fraction, but then this model produces too many intermediate galaxies. Fixing a delay time of 3 Gyr, as suggested from the local Universe, produces too few quiescent galaxies. The observed fractions are best matched with a model that includes a delay that is proportional to the dynamical time and a rapid quenching time-scale (∼0.25 Gyr), but this model also predicts intermediate galaxies Hδ strength higher than that observed. Using stellar synthesis models, we have tested other scenarios, such as the rejuvenation of star formation in early-type galaxies and a portion of quenched galaxies possessing residual star formation. If environment quenching plays a role in the GEEC2 sample, then our work suggests that only a fraction of intermediate galaxies may be undergoing this transition and that quenching occurs quite rapidly in satellite galaxies (≲0.25 Gyr)
Modelling and Interpreting The Effects of Spatial Resolution on Solar Magnetic Field Maps
Different methods for simulating the effects of spatial resolution on
magnetic field maps are compared, including those commonly used for
inter-instrument comparisons. The investigation first uses synthetic data, and
the results are confirmed with {\it Hinode}/SpectroPolarimeter data. Four
methods are examined, one which manipulates the Stokes spectra to simulate
spatial-resolution degradation, and three "post-facto" methods where the
magnetic field maps are manipulated directly. Throughout, statistical
comparisons of the degraded maps with the originals serve to quantify the
outcomes. Overall, we find that areas with inferred magnetic fill fractions
close to unity may be insensitive to optical spatial resolution; areas of
sub-unity fill fractions are very sensitive. Trends with worsening spatial
resolution can include increased average field strength, lower total flux, and
a field vector oriented closer to the line of sight. Further-derived quantities
such as vertical current density show variations even in areas of high average
magnetic fill-fraction. In short, unresolved maps fail to represent the
distribution of the underlying unresolved fields, and the "post-facto" methods
generally do not reproduce the effects of a smaller telescope aperture. It is
argued that selecting a method in order to reconcile disparate spatial
resolution effects should depend on the goal, as one method may better preserve
the field distribution, while another can reproduce spatial resolution
degradation. The results presented should help direct future inter-instrument
comparisons.Comment: Accepted for publication in Solar Physics. The final publication
(including full-resolution figures) will be available at
http://www.springerlink.co
Potato farmer and markets strategies to cope with seasonalities and implications for postharvest losses in eastern Uganda.
European UnionInternational Fund for Agricultural Developmen
Do group dynamics play a role in the evolution of member galaxies?
We examine galaxy groups from the present epoch to z ∼ 1 to explore the impact of group dynamics on galaxy evolution. We use group catalogues from the Sloan Digital Sky Survey (SDSS), the Group Environment and Evolution Collaboration (GEEC) and the high-redshift GEEC2 samples to study how the observed member properties depend on the galaxy stellar mass, group dynamical mass and dynamical state of the host group. We find a strong correlation between the fraction of non-star-forming (quiescent) galaxies and galaxy stellar mass, but do not detect a significant difference in the quiescent fraction with group dynamical mass, within our sample halo mass range of ∼1013–1014.5 M⊙, or with dynamical state. However, at z ∼ 0.4 we do find some evidence that the quiescent fraction in low-mass galaxies [log10(Mstar/M⊙) ≲ 10.5] is lower in groups with substructure. Additionally, our results show that the fraction of groups with non-Gaussian velocity distributions increases with redshift to z ∼ 0.4, while the amount of detected substructure remains constant to z ∼ 1. Based on these results, we conclude that for massive galaxies [log10(Mstar/M⊙) ≳ 10.5], evolution is most strongly correlated to the stellar mass of a galaxy with little or no additional effect related to either the group dynamical mass or the dynamical state. For low-mass galaxies, we do find some evidence of a correlation between the quiescent fraction and the amount of detected substructure, highlighting the need to probe further down the stellar mass function to elucidate the role of environment in galaxy evolution
- …