2,511 research outputs found
Evidence for global cooling in the Late Cretaceous
PublishedArticleThe Late Cretaceous âgreenhouseâ world witnessed a transition from one of the warmest climates of the past 140 million years to cooler conditions, yet still without significant continental ice. Low-latitude sea surface temperature (SST) records are a vital piece of evidence required to unravel the cause of Late Cretaceous cooling, but high-quality data remain illusive. Here, using an organic geochemical palaeothermometer (TEX86), we present a record of SSTs for the CampanianâMaastrichtian interval (~83â66âMa) from hemipelagic sediments deposited on the western North Atlantic shelf. Our record reveals that the North Atlantic at 35â°N was relatively warm in the earliest Campanian, with maximum SSTs of ~35â°C, but experienced significant cooling (~7â°C) after this to <~28â°C during the Maastrichtian. The overall stratigraphic trend is remarkably similar to records of high-latitude SSTs and bottom-water temperatures, suggesting that the cooling pattern was global rather than regional and, therefore, driven predominantly by declining atmospheric pCO2 levels.We gratefully acknowledge funding from the German Science Foundation (DFG Research Stipend Li 2177/1-1 to C.L.), a Royal Society (UK) URF (S.A.R.), a NERC (UK) grant (J.A.L.), a NERC (UK) studentship (K.L.), The Curry Fund of UCL (C.L.), the Cushman Foundation for Foraminiferal Research (J.M. Resig Fellowship to F.F.) and the Spanish Ministerio de Ciencia e InnovaciĂłn project CGL2011-22912, co-financed by the European Regional Development Fund (I.P.-R., J.A.A., J.A.L.). We thank T. Dunkley-Jones and J. Young for assistance in collecting the samples and S. Schouten for providing TEX86L data from Demerara Rise. This paper is dedicated to Ernie Russell, who sadly died after submission of the manuscript
Plankton community respiration and bacterial metabolism in a North Atlantic Shelf Sea during spring bloom development (April 2015)
Spring phytoplankton blooms are important events in Shelf Sea pelagic systems as the increase in carbon production
results in increased food availability for higher trophic levels and the export of carbon to deeper waters
and the sea-floor. It is usually accepted that the increase in phytoplankton abundance and production is followed
by an increase in plankton respiration. However, this expectation is derived from field studies with a low
temporal sampling resolution (5â15 days). In this study we have measured the time course of plankton abundance,
gross primary production, plankton community respiration, respiration of the plankton size classes
(> 0.8 ÎŒm and 0.2â0.8 ÎŒm) and bacterial production at â€5 day intervals during April 2015 in order to examine
the phasing of plankton autotrophic and heterotrophic processes. Euphotic depth-integrated plankton community
respiration increased five-fold (from 22 ± 4 mmol O2mâ2 dâ1 on 4th April to 119 ± 4 mmol O2mâ2 dâ1
on 15th April) at the same time as gross primary production also increased five-fold, (from 114 ± 5 to
613 ± 28 mmol Cmâ2 dâ1). Bacterial production began to increase during the development of the bloom, but
did not reach its maximum until 5 days after the peak in primary production and plankton respiration. The
increase in plankton community respiration was driven by an increase in the respiration attributable to the>
0.8 ÎŒm size fraction of the plankton community (which would include phytoplankton, microzooplankton and
particle attached bacteria). Euphotic depth-integrated respiration of the 0.2â0.8 ÎŒm size fraction (predominantly
free living bacteria) decreased and then remained relatively constant (16 ± 3 â 11 ± 1 mmol O2mâ2 dâ1)
between the first day of sampling (4th April) and the days following the peak in chlorophyll-a (20th and 25th
April). Recent locally synthesized organic carbon was more than sufficient to fulfil the bacterial carbon requirement
in the euphotic zone during this productive period. Changes in bacterial growth efficiencies (BGE, the
ratio of bacterial production to bacterial carbon demand) were driven by changes in bacterial production rates
increasing from<30 ± 14% on 4th April to 51 ± 11% on 25th of April. This study therefore shows a concurrent
rather than a phased increase in primary production and community respiration attributable to
cells>0.8 ÎŒm during the development of the spring bloom, followed 5 days later by a peak in bacterial production.
In addition, the size fractionated respiration rates and high growth efficiencies suggest that free living
bacteria are not the major producers of CO2 before, during and a few days after this shelf sea spring phytoplankton
bloom
Fibronectin matrix-mediated cohesion suppresses invasion of prostate cancer cells
<p>Abstract</p> <p>Background</p> <p>Invasion is an important early step in the metastatic cascade and is the primary cause of death of prostate cancer patients. In order to invade, cells must detach from the primary tumor. Cell-cell and cell-ECM interactions are important regulators of cohesion - a property previously demonstrated to mediate cell detachment and invasion. The studies reported here propose a novel role for α5ÎČ1 integrin - the principle mediator of fibronectin matrix assembly (FNMA) - as an invasion suppressor of prostate cancer cells.</p> <p>Methods</p> <p>Using a combination of biophysical and cell biological methods, and well-characterized prostate cancer cell lines of varying invasiveness, we explore the relationship between cohesion, invasiveness, and FNMA.</p> <p>Results</p> <p>We show that cohesion is inversely proportional to invasive capacity. We also show that more invasive cells express lower levels of α5ÎČ1 integrin and lack the capacity for FNMA. Cells were generated to over-express either wild-type α5 integrin or an integrin in which the cytoplasmic domain of α5 was replaced with that of α2. The α2 construct does not promote FNMA. We show that only wild-type α5 integrin promotes aggregate compaction, increases cohesion, and reduces invasion of the more aggressive cells, and that these effects can be blocked by the 70-kDa fibronectin fragment.</p> <p>Conclusions</p> <p>We propose that restoring capacity for FNMA in deficient cells can increase tumor intercellular cohesion to a point that significantly reduces cell detachment and subsequent invasion. In prostate cancer, this could be of therapeutic benefit by blocking an early key step in the metastatic cascade.</p
Multimodality and Memory in the Mise en page of Guillaume de Machaut's Mass
Guillaume de Machautâs mass survives in only five manuscripts, which all form part of the surprisingly homogeneous âcomplete worksâ set of Machaut manuscripts. In this contribution, I argue that the details of mise en page in these manuscripts are reflective both of scribal memorial processes and multimodality in action: in this work where one of the major modes (image) is absent, the musical notation itself takes on an additional aesthetic role, that of visual beauty. In these manuscripts, the mass takes its place within the music section, surrounded there by lays, motets, virelais, and rondeaux, these surrounded (or preceded) by courtly âditsâ and lyrics not set to music. Four of these five manuscripts are illuminated, and all provide musical notation: all, therefore, are overtly multimodal.
Despite the lavish illumination in the manuscripts, the mass is never adorned with a miniature, nor is it mentioned in Machautâs âPrologueâ to his works. The aesthetic beauty of the mise en page of the mass, therefore, is derived from the musical notation, while the text-music setting shows a distinct divide between the two contrasting compositional techniques of the mass
Two rapid assays for screening of patulin biodegradation
ArtĂculo sobre distintos ensayos para comprobar la biodegradaciĂłn de la patulinaThe mycotoxin patulin is produced by the blue
mould pathogen Penicillium expansum in rotting apples
during postharvest storage. Patulin is toxic to a wide range
of organisms, including humans, animals, fungi and bacteria.
Wash water from apple packing and processing
houses often harbours patulin and fungal spores, which can
contaminate the environment. Ubiquitous epiphytic yeasts,
such as Rhodosporidium kratochvilovae strain LS11 which
is a biocontrol agent of P. expansum in apples, have the
capacity to resist the toxicity of patulin and to biodegrade
it. Two non-toxic products are formed. One is desoxypatulinic
acid. The aim of the work was to develop rapid,
high-throughput bioassays for monitoring patulin degradation
in multiple samples. Escherichia coli was highly
sensitive to patulin, but insensitive to desoxypatulinic acid.
This was utilized to develop a detection test for patulin,
replacing time-consuming thin layer chromatography or
high-performance liquid chromatography. Two assays for patulin degradation were developed, one in liquid medium
and the other in semi-solid medium. Both assays allow the
contemporary screening of a large number of samples. The
liquid medium assay utilizes 96-well microtiter plates and
was optimized for using a minimum of patulin. The semisolid
medium assay has the added advantage of slowing
down the biodegradation, which allows the study and isolation
of transient degradation products. The two assays are
complementary and have several areas of utilization, from
screening a bank of microorganisms for biodegradation
ability to the study of biodegradation pathways
Conformally rescaled spacetimes and Hawking radiation
We study various derivations of Hawking radiation in conformally rescaled
metrics. We focus on two important properties, the location of the horizon
under a conformal transformation and its associated temperature. We find that
the production of Hawking radiation cannot be associated in all cases to the
trapping horizon because its location is not invariant under a conformal
transformation. We also find evidence that the temperature of the Hawking
radiation should transform simply under a conformal transformation, being
invariant for asymptotic observers in the limit that the conformal
transformation factor is unity at their location.Comment: 22 pages, version submitted to journa
Epidemiological, clinical, outcome and antibiotic susceptibility differences between PVL positive and PVL negative Staphylococcus aureus infections in Western Australia: A case control study
Background: Panton Valentine Leukocidin (PVL) has been associated with invasive Staphylococcus aureus soft tissue and pneumonic infections. Methods: From September 2007 to January 2009 at Royal Perth Hospital we tested for the PVL gene in S. aureus isolates from an invasive site, a suspected PVL-related soft tissue infection and all MRSA isolates. We could access medical records for 141 PVL positive (PVL + ve) infections and compared these to a control group comprised of 148 PVL negative (PVL-ve) infections. Results: In the PVL + ve group 62 isolates were MRSA (48 were ST93-MRSA-IV) and 79 isolates were methicillin-sensitive S. aureus, and in the PVL-ve group 56 were MRSA (50 were WA-MRSA strains) and 92 were methicillin-sensitive S. aureus. We found the presence of PVL to be significantly associated with younger age, aboriginality, intravenous drug use, community acquisition, shorter length of hospital stay and lower mortality at 1 year. Overall PVL + ve infections more often required surgical intervention (73.0% versus 44.6%, p < 0.001) and were less often polymicrobial (8.5% versus 41.2%, p < 0.001). PVL + ve isolates were more often susceptible to clindamycin (87.9% versus 73.0%, p = 0.002). Conclusions: This study demonstrates that PVL + ve infections are associated with a distinct clinical picture, predominantly pyogenic skin and soft tissue infections often requiring surgery, disproportionately affecting patients who are younger, indigenous or with fewer health-care risk factors
Fundamental Concepts
This chapter briefly discusses the fundamental properties of black holes in
general relativity, the discovery of astrophysical black holes and their main
astronomical observations, how X-ray and -ray facilities can study
these objects, and ends with a list of open problems and future developments in
the field.Comment: 14 pages, 4 figures. To appear in "Tutorial Guide to X-ray and
Gamma-ray Astronomy: Data Reduction and Analysis" (Ed. C. Bambi, Springer
Singapore, 2020). v2: fixed some typos and updated some parts. arXiv admin
note: text overlap with arXiv:1711.1025
Reproductive abnormalities in mice expressing omega-3 fatty acid desaturase in their mammary glands
The Caenorhabditis elegans n-3 fatty acid desaturase (Fat-1) acts on a range of 18- and 20-carbon n-6 fatty acid substrates. Transgenic female mice expressing the Fat-1 gene under transcriptional control of the goat ÎČ-casein promoter produce milk phospholipids having elevated levels of n-3 polyunsaturated fatty acids (PUFA). However, females from this line were also observed to have impaired reproductive performance characterized by a smaller litter size (2.7 ± 0.6 vs. 7.2 ± 0.7; P < 0.05) than wildtype controls. While there is a close association between PUFA metabolism, prostaglandin biosynthesis, and fertility; reproductive problems in these mice were unanticipated given that the Fat-1 transgene is primarily expressed in the lactating mammary gland. Using multiple approaches it was found that Fat-1 mice have normal ovulation and fertilization rates; however fewer embryos were present in the uterus prior to implantation. Small litter size was also found to be partly attributable to a high incidence of post-implantation fetal resorptions. Embryo transfer experiments revealed that embryos developing from oocytes derived from transgenic ovaries had an increased rate of post-implantation resorption, regardless of the uterine genotype. Ovary transplantation between Fat-1 and C57BL/6 wildtype females revealed that non-ovarian factors also contributed to the smaller litter size phenotype. Finally, surgical removal of the mammary glands from juvenile Fat-1 mice increased the subsequent number of implantation sites per female, but did not lessen the high rate of post-implantation resorptions. In conclusion, we herein report on a system where an exogenous transgene expressed predominately in the mammary gland detrimentally affects female reproduction, suggesting that in certain circumstances the mammary gland may function as an endocrine regulator of reproductive performance
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