1,665 research outputs found
Test code for the assessment and improvement of Reynolds stress models
An existing two-dimensional, compressible flow, Navier-Stokes computer code, containing a full Reynolds stress turbulence model, was adapted for use as a test bed for assessing and improving turbulence models based on turbulence simulation experiments. To date, the results of using the code in comparison with simulated channel flow and over an oscillating flat plate have shown that the turbulence model used in the code needs improvement for these flows. It is also shown that direct simulation of turbulent flows over a range of Reynolds numbers are needed to guide subsequent improvement of turbulence models
Clinical Dilemma in the Treatment of a Patient with Microangiopathic Haemolytic Anaemia, Thrombocytopaenia and Severe Hypertension
While haemolytic uraemic syndrome in children is predominantly associated with Shiga toxin -producing Escherichia coli (typically 0157:H7), some cases occur without associated diarrhoea, or as the manifestation of an underlying disorder other than infection.
Haemolytic uraemic syndrome is characterised
by microangiopathic anaemia, thrombocytopaenia
and renal failure, on occasion accompanied by severe hypertension. Malignant hypertension is a syndrome that sometimes exhibits the same laboratory abnormalities
as haemolytic uraemic syndrome as it may
share the same pathological findings: thrombotic microangiopathy. As clinical features of both entities overlap, the distinction between them can be very
difficult. However, differentiation is essential for the treatment decision, since early plasma exchange dramatically reduces mortality in haemolytic uraemic syndrome not associated with diarrhoea. An increasing
number of genetic causes of this pathology have been described and may be very useful in differentiating it from thrombotic microangiopathy due to other aetiologies. Despite advances in the understanding
of the pathophysiology of haemolytic uraemic
syndrome not associated with diarrhoea, the
management often remains empirical. We describe a patient with simultaneous microangiopathic haemolytic
anaemia, thrombocytopaenia and severe hypertension managed in the acute period of illness with plasma exchange
The Closest Damped Lyman Alpha System
A difficulty of studying damped Lyman alpha systems is that they are distant,
so one knows little about the interstellar medium of the galaxy. Here we report
upon a damped Lyman alpha system in the nearby galaxy NGC 4203, which is so
close (v_helio = 1117 km/s) and bright (B_o = 11.62) that its HI disk has been
mapped. The absorption lines are detected against Ton 1480, which lies only
1.9' (12 h_50 kpc) from the center of NGC 4203. Observations were obtained with
the Faint Object Spectrograph on HST (G270H grating) over the 2222-3277
Angstrom region with 200 km/s resolution. Low ionization lines of Fe, Mn, and
Mg were detected, leading to metallicities of -2.29, -2.4, which
are typical of other damped Lyman alpha systems, but well below the stellar
metallicity of this type of galaxy. Most notably, the velocity of the lines is
1160 +- 10 km/s, which is identical to the HI rotational velocity of 1170 km/s
at that location in NGC 4203, supporting the view that these absorption line
systems can be associated with the rotating disks of galaxies. In addition, the
line widths of the Mg lines give an upper limit to the velocity dispersion of
167 km/s, to the 99% confidence level.Comment: 4 pages LaTeX, including 1 figure and 1 table, uses emulateapj.sty.
Accepted for publication by Astrophysical Journal Letter
A dual role for GRP in cardiovascular disease
Management and prevention of cardiovascular disease (CVD) represents one of the major health challenges worldwide. CVD is the leading cause of death globally despite all research efforts on last decades regarding the molecular mechanisms and processes involved on its development and progression. Chronic Kidney Disease (CKD) is an independent risk factor and promotor of CVD events, representing a considerable economic cost for the health system. CVD is the leading cause of death in all CKD stages, accounting for half the number of deaths in this population.info:eu-repo/semantics/publishedVersio
Retrotransposons represent the most labile fraction for genomic rearrangements in polyploid plant species
Understanding how increased genome size and diversity
within polyploid genomes impacts plant evolution and
breeding continues to be challenging. Although historical
studies by McClintock suggested the importance of transposable
elements mediated by polyploidisation on genomic
changes, data from plant crosses remain scarce. Despite the
absence of a conclusive proof regarding autonomous retrotransposon
movement in synthetic allopolyploids, the
transposition of retrotransposons and their ubiquitous dispersion
in all plant species might explain the positive correlation
between the genome size of plants and the prevalence
of retrotransposons. Here, we address polyploidisationmediated
rearrangements of retrotransposon-associated sequences
and discuss a tendency for a preferential restructuring
of large ancestral genomes after polyploidisation. A
comparative analysis of the frequency of modifications of
retrotransposon-associated sequences in synthetic polyploids
with marked differences in genome sizes is presented.
Such analyses suggest the absence of a significant difference
in the rates of rearrangements despite vast dissimilarities in
the retrotransposon copy number between species, which emphasises the high plasticity of this genomic feature. See
also the sister article focusing on animals by Arkhipova and
Rodriguez in this themed issu
Differential effects of high-temperature stress on nuclear topology and transcription of repetitive noncoding and coding rye sequences
The plant stress response has been extensively characterized
at the biochemical and physiological levels. However, knowledge
concerning repetitive sequence genome fraction modulation
during extreme temperature conditions is scarce. We
studied high-temperature effects on subtelomeric repetitive
sequences (pSc200) and 45S rDNA in rye seedlings submitted
to 40 ° C during 4 h. Chromatin organization patterns were
evaluated through fluorescent in situ hybridization and transcription
levels were assessed using quantitative real-time
PCR. Additionally, the nucleolar dynamics were evaluated
through fibrillarin immunodetection in interphase nuclei.
The results obtained clearly demonstrated that the pSc200
sequence organization is not affected by high-temperature
stress (HTS) and proved for the first time that this noncoding
subtelomeric sequence is stably transcribed. Conversely, it
was demonstrated that HTS treatment induces marked rDNA
chromatin decondensation along with nucleolar enlargement
and a significant increase in ribosomal gene transcription.
The role of noncoding and coding repetitive rye sequences
in the plant stress response that are suggested by
their clearly distinct behaviors is discussed. While the hetero-chromatic conformation of pSc200 sequences seems to be
involved in the stabilization of the interphase chromatin architecture
under stress conditions, the dynamic modulation
of nucleolar and rDNA topology and transcription suggest
their role in plant stress response pathway
Unravelling genome dynamics in Arabidopsis synthetic auto and allopolyploid species
Polyploidization is a major genome modification that results in plant species with multiple chromosome sets. Parental
genome adjustment to co-habit a new nuclear environment results in additional innovation outcomes. We intended to
assess genomic changes in polyploid model species with small genomes using inter retrotransposons amplified
polymorphism (IRAP) and retrotransposon microsatellite amplified polymorphism (REMAP). Comparative analysis
among diploid and autotetraploid A. thaliana and A. suecica lines with their parental lines revealed a marginal fraction
of novel bands in both polyploids, and a vast loss of parental bands in allopolyploids. Sequence analysis of some
remodelled bands shows that A. suecica parental band losses resulted mainly from sequence changes restricted to primer
domains. Moreover, in A. suecica, both parental genomes presented rearrangement frequencies proportional to their
sizes. Overall rates of genomic remodelling events detected in A. suecica were similar to those observed in species with
a large genome supporting the role of retrotransposons and microsatellite sequences in the evolution of most
allopolyploidsAcknowledgements: M. Bento was funded by a FCT (Fundação para a CiĂȘncia e a Tecnologia, Portugal) postdoctoral grant
(SFRH/BPD/80550/2011), Diana TomĂĄs was funded by a FCT doctoral scholarship (SFRH/BD/93156/2013), Manuela Silva by the
FCT Investigator Programme (IF/00834/2014), and the research work was financed by FCT LEAF Unit (UID/AGR/04129/2013)
Temperature Fluctuations and Abundances in HII Galaxies
There is evidence for temperature fluctuations in Planetary Nebulae and in
Galactic HII regions. If such fluctuations occur in the low-metallicity,
extragalactic HII regions used to probe the primordial helium abundance, the
derived 4He mass fraction, Y_P, could be systematically different from the true
primordial value. For cooler, mainly high-metallicity HII regions the derived
helium abundance may be nearly unchanged but the oxygen abundance could have
been seriously underestimated. For hotter, mainly low-metallicity HII regions
the oxygen abundance is likely accurate but the helium abundance could be
underestimated. The net effect is to tilt the Y vs. Z relation, making it
flatter and resulting in a higher inferred Y_P. Although this effect could be
large, there are no data which allow us to estimate the size of the temperature
fluctuations for the extragalactic HII regions. Therefore, we have explored
this effect via Monte Carlos in which the abundances derived from a fiducial
data set are modified by \Delta-T chosen from a distribution with 0 < \Delta-T
< \Delta-T_max where \Delta-T_max is varied from 500K to 4000K. It is
interesting that although this effect shifts the locations of the HII regions
in Y vs. O/H plane, it does not introduce any significant additional
dispersion.Comment: 11 pages, 9 postscript figures; submitted to the Ap
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