293 research outputs found
The collision of boosted black holes
We study the radiation from a collision of black holes with equal and
opposite linear momenta. Results are presented from a full numerical relativity
treatment and are compared with the results from a ``close-slow''
approximation. The agreement is remarkable, and suggests several insights about
the generation of gravitational radiation in black hole collisions.Comment: 8 pages, RevTeX, 3 figures included with eps
Recommended from our members
MicroRNA expression profiling of human breast cancer identifies new markers of tumor subtype.
BACKGROUND: MicroRNAs (miRNAs), a class of short non-coding RNAs found in many plants and animals, often act post-transcriptionally to inhibit gene expression. RESULTS: Here we report the analysis of miRNA expression in 93 primary human breast tumors, using a bead-based flow cytometric miRNA expression profiling method. Of 309 human miRNAs assayed, we identify 133 miRNAs expressed in human breast and breast tumors. We used mRNA expression profiling to classify the breast tumors as luminal A, luminal B, basal-like, HER2+ and normal-like. A number of miRNAs are differentially expressed between these molecular tumor subtypes and individual miRNAs are associated with clinicopathological factors. Furthermore, we find that miRNAs could classify basal versus luminal tumor subtypes in an independent data set. In some cases, changes in miRNA expression correlate with genomic loss or gain; in others, changes in miRNA expression are likely due to changes in primary transcription and or miRNA biogenesis. Finally, the expression of DICER1 and AGO2 is correlated with tumor subtype and may explain some of the changes in miRNA expression observed. CONCLUSION: This study represents the first integrated analysis of miRNA expression, mRNA expression and genomic changes in human breast cancer and may serve as a basis for functional studies of the role of miRNAs in the etiology of breast cancer. Furthermore, we demonstrate that bead-based flow cytometric miRNA expression profiling might be a suitable platform to classify breast cancer into prognostic molecular subtypes.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
Breaking the waves: improved detection of copy number variation from microarray-based comparative genomic hybridization.
BACKGROUND: Large-scale high throughput studies using microarray technology have established that copy number variation (CNV) throughout the genome is more frequent than previously thought. Such variation is known to play an important role in the presence and development of phenotypes such as HIV-1 infection and Alzheimer's disease. However, methods for analyzing the complex data produced and identifying regions of CNV are still being refined. RESULTS: We describe the presence of a genome-wide technical artifact, spatial autocorrelation or 'wave', which occurs in a large dataset used to determine the location of CNV across the genome. By removing this artifact we are able to obtain both a more biologically meaningful clustering of the data and an increase in the number of CNVs identified by current calling methods without a major increase in the number of false positives detected. Moreover, removing this artifact is critical for the development of a novel model-based CNV calling algorithm - CNVmix - that uses cross-sample information to identify regions of the genome where CNVs occur. For regions of CNV that are identified by both CNVmix and current methods, we demonstrate that CNVmix is better able to categorize samples into groups that represent copy number gains or losses. CONCLUSION: Removing artifactual 'waves' (which appear to be a general feature of array comparative genomic hybridization (aCGH) datasets) and using cross-sample information when identifying CNVs enables more biological information to be extracted from aCGH experiments designed to investigate copy number variation in normal individuals.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
MicroRNA expression profiling of human breast cancer identifies new markers of tumor subtype
Integrated analysis of miRNA expression and genomic changes in human breast tumors allows the classification of tumor subtypes
Galaxy and mass assembly (GAMA): the inferred massâmetallicity relation from z = 0 to 3.5 via forensic SED fitting
We analyse the metallicity histories of âŒ4500 galaxies from the GAMA survey at z \u3c 0.06 modelled by the SED-fitting code PROSPECT using an evolving metallicity implementation. These metallicity histories, in combination with the associated star formation histories, allow us to analyse the inferred gas-phase massâmetallicity relation. Furthermore, we extract the massâ metallicity relation at a sequence of epochs in cosmic history, to track the evolving massâmetallicity relation with time. Through comparison with observations of gas-phase metallicity over a large range of redshifts, we show that, remarkably, our forensic SED analysis has produced an evolving massâmetallicity relationship that is consistent with observations at all epochs. We additionally analyse the three-dimensional massâmetallicityâSFR space, showing that galaxies occupy a clearly defined plane. This plane is shown to be subtly evolving, displaying an increased tilt with time caused by general enrichment, and also the slowing down of star formation with cosmic time. This evolution is most apparent at lookback times greater than 7 Gyr. The trends in metallicity recovered in this work highlight that the evolving metallicity implementation used within the SED-fitting code PROSPECT produces reasonable metallicity results over the history of a galaxy. This is expected to provide a significant improvement to the accuracy of the SED-fitting outputs
High-resolution aCGH and expression profiling identifies a novel genomic subtype of ER negative breast cancer.
BACKGROUND: The characterization of copy number alteration patterns in breast cancer requires high-resolution genome-wide profiling of a large panel of tumor specimens. To date, most genome-wide array comparative genomic hybridization studies have used tumor panels of relatively large tumor size and high Nottingham Prognostic Index (NPI) that are not as representative of breast cancer demographics. RESULTS: We performed an oligo-array-based high-resolution analysis of copy number alterations in 171 primary breast tumors of relatively small size and low NPI, which was therefore more representative of breast cancer demographics. Hierarchical clustering over the common regions of alteration identified a novel subtype of high-grade estrogen receptor (ER)-negative breast cancer, characterized by a low genomic instability index. We were able to validate the existence of this genomic subtype in one external breast cancer cohort. Using matched array expression data we also identified the genomic regions showing the strongest coordinate expression changes ('hotspots'). We show that several of these hotspots are located in the phosphatome, kinome and chromatinome, and harbor members of the 122-breast cancer CAN-list. Furthermore, we identify frequently amplified hotspots on 8q22.3 (EDD1, WDSOF1), 8q24.11-13 (THRAP6, DCC1, SQLE, SPG8) and 11q14.1 (NDUFC2, ALG8, USP35) associated with significantly worse prognosis. Amplification of any of these regions identified 37 samples with significantly worse overall survival (hazard ratio (HR) = 2.3 (1.3-1.4) p = 0.003) and time to distant metastasis (HR = 2.6 (1.4-5.1) p = 0.004) independently of NPI. CONCLUSION: We present strong evidence for the existence of a novel subtype of high-grade ER-negative tumors that is characterized by a low genomic instability index. We also provide a genome-wide list of common copy number alteration regions in breast cancer that show strong coordinate aberrant expression, and further identify novel frequently amplified regions that correlate with poor prognosis. Many of the genes associated with these regions represent likely novel oncogenes or tumor suppressors.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
Deep Extragalactic VIsible Legacy Survey (DEVILS): SED fitting in the D10-COSMOS field and the evolution of the stellar mass function and SFRâMâ relation
We present catalogues of stellar masses, star formation rates (SFRs), and ancillary stellar population parameters for galaxies spanning 0 \u3c z \u3c 9 from the Deep Extragalactic VIsible Legacy Survey (DEVILS). DEVILS is a deep spectroscopic redshift survey with very high completeness, covering several premier deep fields including COSMOS (D10). Our stellar mass and SFR estimates are self-consistently derived using the spectral energy distribution (SED) modelling code PROSPECT, using well-motivated parametrizations for dust attenuation, star formation histories, and metallicity evolution. We show how these improvements, and especially our physically motivated assumptions about metallicity evolution, have an appreciable systematic effect on the inferred stellar masses, at the level of âŒ0.2 dex. To illustrate the scientific value of these data, we map the evolving galaxy stellar mass function (SMF) and the SFRâMâ relation for 0 \u3c z \u3c 4.25. In agreement with past studies, we find that most of the evolution in the SMF is driven by the characteristic density parameter, with little evolution in the characteristic mass and low-mass slopes. Where the SFRâMâ relation is indistinguishable from a power law at z \u3e 2.6, we see evidence of a bend in the relation at low redshifts (z \u3c 0.45). This suggests evolution in both the normalization and shape of the SFRâMâ relation since cosmic noon. It is significant that we only clearly see this bend when combining our new DEVILS measurements with consistently derived values for lower redshift galaxies from the Galaxy And Mass Assembly (GAMA) survey: this shows the power of having consistent treatment for galaxies at all redshifts
Wilsonian Approach to Fluid/Gravity Duality
The problem of gravitational fluctuations confined inside a finite cutoff at
radius outside the horizon in a general class of black hole geometries
is considered. Consistent boundary conditions at both the cutoff surface and
the horizon are found and the resulting modes analyzed. For general cutoff
the dispersion relation is shown at long wavelengths to be that of a
linearized Navier-Stokes fluid living on the cutoff surface. A cutoff-dependent
line-integral formula for the diffusion constant is derived. The
dependence on is interpreted as renormalization group (RG) flow in the
fluid. Taking the cutoff to infinity in an asymptotically AdS context, the
formula for reproduces as a special case well-known results derived
using AdS/CFT. Taking the cutoff to the horizon, the effective speed of sound
goes to infinity, the fluid becomes incompressible and the Navier-Stokes
dispersion relation becomes exact. The resulting universal formula for the
diffusion constant reproduces old results from the membrane
paradigm. Hence the old membrane paradigm results and new AdS/CFT results are
related by RG flow. RG flow-invariance of the viscosity to entropy ratio is shown to follow from the first law of thermodynamics together with
isentropy of radial evolution in classical gravity. The ratio is expected to
run when quantum gravitational corrections are included.Comment: 34 pages, harvmac, clarified boundary conditio
Deep Extragalactic VIsible Legacy Survey (DEVILS): SED Fitting in the D10-COSMOS Field and the Evolution of the Stellar Mass Function and SFR- relation
We present catalogues of stellar masses, star formation rates, and ancillary
stellar population parameters for galaxies spanning from the Deep
Extragalactic VIsible Legacy Survey (DEVILS). DEVILS is a deep spectroscopic
redshift survey with very high completeness, covering several premier deep
fields including COSMOS (D10). Our stellar mass and star formation rate
estimates are self-consistently derived using the spectral energy distribution
(SED) modeling code ProSpect, using well-motivated parameterisations for dust
attenuation, star formation histories, and metallicity evolution. We show how
these improvements, and especially our physically motivated assumptions about
metallicity evolution, have an appreciable systematic effect on the inferred
stellar masses, at the level of 0.2 dex. To illustrate the scientific
value of these data, we map the evolving galaxy stellar mass function (SMF) for
and the SFR- relation for . In agreement with past
studies, we find that most of the evolution in the SMF is driven by the
characteristic density parameter, with little evolution in the characteristic
mass and low-mass slopes. Where the SFR- relation is indistinguishable
from a power-law at , we see evidence of a bend in the relation at low
redshifts (). This suggests evolution in both the normalisation and
shape of the SFR- relation since cosmic noon. It is significant that
we only clearly see this bend when combining our new DEVILS measurements with
consistently derived values for lower redshift galaxies from the Galaxy And
Mass Assembly (GAMA) survey: this shows the power of having consistent
treatment for galaxies at all redshifts.Comment: Submitted for publication in MNRA
Can the Gravitational Wave Background from Inflation be Detected Locally?
The Cosmic Background Explorer (COBE) detection of microwave background
anisotropies may contain a component due to gravitational waves generated by
inflation. It is shown that the gravitational waves from inflation might be
seen using `beam-in-space' detectors, but not the Laser Interferometer Gravity
Wave Observatory (LIGO). The central conclusion, dependent only on weak
assumptions regarding the physics of inflation, is a surprising one. The larger
the component of the COBE signal due to gravitational waves, the {\em smaller}
the expected local gravitational wave signal.Comment: 8 pages, standard LaTeX (no figures), SUSSEX-AST 93/7-
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