An extreme critical space-time: echoing and black-hole perturbations

A homothetic, static, spherically symmetric solution to the massless Einstein- Klein-Gordon equations is described. There is a curvature singularity which is central, null, bifurcate and marginally trapped. The space-time is therefore extreme in the sense of lying at the threshold between black holes and naked singularities, just avoiding both. A linear perturbation analysis reveals two types of dominant mode. One breaks the continuous self-similarity by periodic terms reminiscent of discrete self-similarity, with echoing period within a few percent of the value observed numerically in near-critical gravitational collapse. The other dominant mode explicitly produces a black hole, white hole, eternally naked singularity or regular dispersal, the latter indicating that the background is critical. The black hole is not static but has constant area, the corresponding mass being linear in the perturbation amplitudes, explicitly determining a unit critical exponent. It is argued that a central null singularity may be a feature of critical gravitational collapse.Comment: 6 revtex pages, 6 eps figure

Efficient Photon Upconversion Enabled by Strong Coupling Between Organic Molecules and Quantum Dots

Hybrid structures formed between organic molecules and inorganic quantum dots can accomplish unique photophysical transformations by taking advantage of their disparate properties. The electronic coupling between these materials is typically weak, leading photoexcited charge carriers to spatially localize to a dot or a molecule at its surface. However, we show that by converting a chemical linker that covalently binds anthracene molecules to silicon quantum dots from a carbon-carbon single bond to a double bond, we access a strong-coupling regime where excited carriers spatially delocalize across both anthracene and silicon. By pushing the system to delocalize, we design a photon upconversion system with a higher efficiency (17.2%) and lower threshold intensity (0.5 W/cm^2) than that of a corresponding weakly-coupled system. Our results show that strong coupling between molecules and nanostructures achieved through targeted linking chemistry provides a new route for tailoring properties in materials for light-driven applications.Comment: 33 pages (20 in main text, 13 in supporting information), 12 figures (5 in main text, 7 in supporting information

WT1 and its transcriptional cofactor BASP1 redirect the differentiation pathway of an established blood cell line

The Wilms' tumour suppressor WT1 (Wilms' tumour 1) is a transcriptional regulator that plays a central role in organogenesis, and is mutated or aberrantly expressed in several childhood and adult malignancies. We previously identified BASP1 (brain acid-soluble protein 1) as a WT1 cofactor that suppresses the transcriptional activation function of WT1. In the present study we have analysed the dynamic between WT1 and BASP1 in the regulation of gene expression in myelogenous leukaemia K562 cells. Our findings reveal that BASP1 is a significant regulator of WT1 that is recruited to WT1-binding sites and suppresses WT1-mediated transcriptional activation at several WT1 target genes. We find that WT1 and BASP1 can divert the differentiation programme of K562 cells to a non-blood cell type following induction by the phorbol ester PMA. WT1 and BASP1 co-operate to induce the differentiation of K562 cells to a neuronal-like morphology that exhibits extensive arborization, and the expression of several genes involved in neurite outgrowth and synapse formation. Functional analysis revealed the relevance of the transcriptional reprogramming and morphological changes, in that the cells elicited a response to the neurotransmitter ATP. Taken together, the results of the present study reveal that WT1 and BASP1 can divert the lineage potential of an established blood cell line towards a cell with neuronal characteristics

WT1 and its transcriptional cofactor BASP1 redirect the differentiation pathway of an established blood cell line

The Wilms' tumour suppressor WT1 (Wilms' tumour 1) is a transcriptional regulator that plays a central role in organogenesis, and is mutated or aberrantly expressed in several childhood and adult malignancies. We previously identified BASP1 (brain acid-soluble protein 1) as a WT1 cofactor that suppresses the transcriptional activation function of WT1. In the present study we have analysed the dynamic between WT1 and BASP1 in the regulation of gene expression in myelogenous leukaemia K562 cells. Our findings reveal that BASP1 is a significant regulator of WT1 that is recruited to WT1-binding sites and suppresses WT1-mediated transcriptional activation at several WT1 target genes. We find that WT1 and BASP1 can divert the differentiation programme of K562 cells to a non-blood cell type following induction by the phorbol ester PMA. WT1 and BASP1 co-operate to induce the differentiation of K562 cells to a neuronal-like morphology that exhibits extensive arborization, and the expression of several genes involved in neurite outgrowth and synapse formation. Functional analysis revealed the relevance of the transcriptional reprogramming and morphological changes, in that the cells elicited a response to the neurotransmitter ATP. Taken together, the results of the present study reveal that WT1 and BASP1 can divert the lineage potential of an established blood cell line towards a cell with neuronal characteristics

The GALEX Arecibo SDSS Survey. I. Gas Fraction Scaling Relations of Massive Galaxies and First Data Release

We introduce the GALEX Arecibo SDSS Survey (GASS), an on-going large program that is gathering high quality HI-line spectra using the Arecibo radio telescope for an unbiased sample of ~1000 galaxies with stellar masses greater than 10^10 Msun and redshifts 0.025<z<0.05, selected from the SDSS spectroscopic and GALEX imaging surveys. The galaxies are observed until detected or until a low gas mass fraction limit (1.5-5%) is reached. This paper presents the first Data Release, consisting of ~20% of the final GASS sample. We use this data set to explore the main scaling relations of HI gas fraction with galaxy structure and NUV-r colour. A large fraction (~60%) of the galaxies in our sample are detected in HI. We find that the atomic gas fraction decreases strongly with stellar mass, stellar surface mass density and NUV-r colour, but is only weakly correlated with galaxy bulge-to-disk ratio (as measured by the concentration index of the r-band light). We also find that the fraction of galaxies with significant (more than a few percent) HI decreases sharply above a characteristic stellar surface mass density of 10^8.5 Msun kpc^-2. The fraction of gas-rich galaxies decreases much more smoothly with stellar mass. One of the key goals of GASS is to identify and quantify the incidence of galaxies that are transitioning between the blue, star-forming cloud and the red sequence of passively-evolving galaxies. Likely transition candidates can be identified as outliers from the mean scaling relations between gas fraction and other galaxy properties. [abridged]Comment: 25 pages, 12 figures. Accepted for publication in MNRAS. Version with high resolution figures available at http://www.mpa-garching.mpg.de/GASS/pubs.ph

The GALEX Arecibo SDSS Survey II: The Star Formation Efficiency of Massive Galaxies

We use measurements of the HI content, stellar mass and star formation rates in ~190 massive galaxies with stellar masses greater than 10^10 Msun, obtained from the Galex Arecibo SDSS Survey (GASS) described in Paper I (Catinella et al. 2010) to explore the global scaling relations associated with the bin-averaged ratio of the star formation rate over the HI mass, which we call the HI-based star formation efficiency (SFE). Unlike the mean specific star formation rate, which decreases with stellar mass and stellar mass surface density, the star formation efficiency remains relatively constant across the sample with a value close to SFE = 10^-9.5 yr^-1 (or an equivalent gas consumption timescale of ~3 Gyr). Specifically, we find little variation in SFE with stellar mass, stellar mass surface density, NUV-r color and concentration. We interpret these results as an indication that external processes or feedback mechanisms that control the gas supply are important for regulating star formation in massive galaxies. An investigation into the detailed distribution of SFEs reveals that approximately 5% of the sample shows high efficiencies with SFE > 10^-9 yr^-1, and we suggest that this is very likely due to a deficiency of cold gas rather than an excess star formation rate. Conversely, we also find a similar fraction of galaxies that appear to be gas-rich for their given specific star-formation rate, although these galaxies show both a higher than average gas fraction and lower than average specific star formation rate. Both of these populations are plausible candidates for "transition" galaxies, showing potential for a change (either decrease or increase) in their specific star formation rate in the near future. We also find that 36+/-5% of the total HI mass density and 47+/-5% of the total SFR density is found in galaxies with stellar mass greater than 10^10 Msun. [abridged]Comment: 18 pages, 11 figures. Accepted for publication in MNRAS. GASS publications and released data can be found at http://www.mpa-garching.mpg.de/GASS/index.ph

Cell size is a determinant of stem cell potential during aging

Stem cells are remarkably small. Whether small size is important for stem cell function is unknown. We find that hematopoietic stem cells (HSCs) enlarge under conditions known to decrease stem cell function. This decreased fitness of large HSCs is due to reduced proliferation and was accompanied by altered metabolism. Preventing HSC enlargement or reducing large HSCs in size averts the loss of stem cell potential under conditions causing stem cell exhaustion. Last, we show that murine and human HSCs enlarge during aging. Preventing this age-dependent enlargement improves HSC function. We conclude that small cell size is important for stem cell function in vivo and propose that stem cell enlargement contributes to their functional decline during aging.Peer reviewe

Gefitinib and <i>EGFR</i> Gene Copy Number Aberrations in Esophageal Cancer

Purpose: The cancer esophagus gefitinib (COG) trial demonstrated improved progression free survival with the Epidermal Growth Factor Receptor (EGFR) tyrosine kinase inhibitor (TKI), gefitinib relative to placebo in advanced esophageal cancer patients with disease progression after chemotherapy. Rapid and durable responses were observed in a minority. We hypothesised that genetic aberration of the EGFR pathway would identify patients benefitting from gefitinib. Patients and Methods: A pre-specified blinded molecular analysis of COG trial tumours was conducted to compare efficacy of gefitinib to placebo according to EGFR copy number gain (CNG) and EGFR, KRAS, BRAF and PIK3CA mutation status. EGFR CNG was determined by fluorescent insitu hybridisation (FISH) using pre-specified criteria and EGFR FISH positive defined as high polysomy or amplification. Results: Biomarker data were available for 340 patients. In EGFR FISH positive tumours (20.2%) overall survival was improved with gefitinib compared to placebo (hazard ratio [HR] for death, 0.59; 95% confidence interval [CI], 0.35, 1.00 p=0.05). In EGFR FISH negative tumours there was no difference in overall survival with gefitinib compared to placebo (HR for death, 0.90, 95% CI 0.69, 1.18 p=0.46). EGFR amplification (7.2%) patients gained greatest benefit from gefitinib (HR for death, 0.21; 95% CI 0.07-0.64; p=0.006). There was no difference in overall survival for gefitinib versus placebo for patients with EGFR, KRAS, BRAF and PIK3CA mutations, or for any mutation versus none. Conclusion: EGFR CNG assessed by FISH appears to identify a subgroup of esophageal cancer patients who may benefit from gefitinib as a second line treatment, and suggests that anti-EGFR 3 therapies should be investigated in prospective clinical trials in different settings in EGFR FI SH positive, and in particular EGFR amplified, esophageal cancer

The Spatial Expansion and Ecological Footprint of Fisheries (1950 to Present)

Using estimates of the primary production required (PPR) to support fisheries catches (a measure of the footprint of fishing), we analyzed the geographical expansion of the global marine fisheries from 1950 to 2005. We used multiple threshold levels of PPR as percentage of local primary production to define ‘fisheries exploitation’ and applied them to the global dataset of spatially-explicit marine fisheries catches. This approach enabled us to assign exploitation status across a 0.5° latitude/longitude ocean grid system and trace the change in their status over the 56-year time period. This result highlights the global scale expansion in marine fisheries, from the coastal waters off North Atlantic and West Pacific to the waters in the Southern Hemisphere and into the high seas. The southward expansion of fisheries occurred at a rate of almost one degree latitude per year, with the greatest period of expansion occurring in the 1980s and early 1990s. By the mid 1990s, a third of the world's ocean, and two-thirds of continental shelves, were exploited at a level where PPR of fisheries exceed 10% of PP, leaving only unproductive waters of high seas, and relatively inaccessible waters in the Arctic and Antarctic as the last remaining ‘frontiers.’ The growth in marine fisheries catches for more than half a century was only made possible through exploitation of new fishing grounds. Their rapidly diminishing number indicates a global limit to growth and highlights the urgent need for a transition to sustainable fishing through reduction of PPR

Fruit crops: a summary of research, 1998

Pesticide deposition in orchards: effects of pesticide type, tree canopy, timing, cultivar, and leaf type / Franklin R. Hall, Jane A. Cooper, and David C. Ferree -- The influence of a synthetic foraging attractant, Bee-Scent™, on the number of honey bees visiting apple blossoms and on subsequent fruit production / James E. Tew and David C. Ferree -- The reliability of three traps vs. a single trap for determining population levels of codling moth in commercial northern Ohio apple orchards / Ted W. Gastier -- Evaluation of an empirical model for predicting sooty blotch and flyspeck of apples in Ohio / Michael A. Ellis, Laurence V. Madden, and L. Lee Wilson -- Influence of pesticides and water stress on photosynthesis and transpiration of apple / David C. Ferree, Franklin R. Hall, Charles R. Krause, Bruce R. Roberts, and Ross D. Brazee -- Influence of temporary bending and heading on branch development and flowering of vigorous young apple trees / David C. Ferree and John C. Schmid -- The effect of apple fruit bruising on total returns / Richard C. Funt, Ewen A. Cameron, and Nigel H. Banks -- Yield, berry quality, and economics of mechanical berry harvest in Ohio / Richard C. Funt, Thomas E. Wall, and Joseph C. Scheerens -- Monitoring flower thrips activities in strawberry fields at two Ohio locations / Roger N. Williams, M. Sean Ellis, Dan S. Fickle, and Carl M. Pelland -- Cluster thinning effects on fruit weight, juice quality, and fruit skin characteristics in 'Reliance' grapes / Yu Gao and Garth A. Cahoon -- Effects of various fungicide programs on powdery mildew control, percent berry sugar, yield, and vine vigor of 'Concord' grapes in Ohio / Michael A. Ellis, Laurence V. Madden, L. Lee Wilson, and Gregory R. Johns -- Influence of growth regulators, cropping, and number on replacement trunks of winter-injured 'Vidal Blanc' grapes / David C. Ferree, David M. Scurlock, and Rick Evans -- Effect of new herbicides on tissue-cultured black raspberry plants / Richard C. Funt, Thomas E. Wall, and B. Dale Stokes -- Investigating the relationship between vine vigor and berry set of field-grown 'Seyval Blanc' grapevines / Steven J. McArtney and David C. Ferree -- Summary of Ohio Fruit Growers Society apple cider competition, 1993-1997 / Winston Bash and Diane Mille