366 research outputs found
Serum levels and removal by haemodialysis and haemodiafiltration of tryptophan-derived uremic toxins in ESKD patients
Tryptophan is an essential dietary amino acid that originates uremic toxins that contribute to end-stage kidney disease (ESKD) patient outcomes. We evaluated serum levels and removal during haemodialysis and haemodiafiltration of tryptophan and tryptophan-derived uremic toxins, indoxyl sulfate (IS) and indole acetic acid (IAA), in ESKD patients in different dialysis treatment settings. This prospective multicentre study in four European dialysis centres enrolled 78 patients with ESKD. Blood and spent dialysate samples obtained during dialysis were analysed with high-performance liquid chromatography to assess uremic solutes, their reduction ratio (RR) and total removed solute (TRS). Mean free serum tryptophan and IS concentrations increased, and concentration of IAA decreased over pre-dialysis levels (67%, 49%, -0.8%, respectively) during the first hour of dialysis. While mean serum total urea, IS and IAA concentrations decreased during dialysis (-72%, -39%, -43%, respectively), serum tryptophan levels increased, resulting in negative RR (-8%) towards the end of the dialysis session (p < 0.001), despite remarkable Trp losses in dialysate. RR and TRS values based on serum (total, free) and dialysate solute concentrations were lower for conventional low-flux dialysis (p < 0.001). High-efficiency haemodiafiltration resulted in 80% higher Trp losses than conventional low-flux dialysis, despite similar neutral Trp RR values. In conclusion, serum Trp concentrations and RR behave differently from uremic solutes IS, IAA and urea and Trp RR did not reflect dialysis Trp losses. Conventional low-flux dialysis may not adequately clear Trp-related uremic toxins while high efficiency haemodiafiltration increased Trp losses
Observations of the Hubble Deep Field with the Infrared Space Observatory. I. Data reduction, maps and sky coverage
We present deep imaging at 6.7 micron and 15 micron from the CAM instrument
on the Infrared Space Observatory (ISO), centred on the Hubble Deep Field
(HDF). These are the deepest integrations published to date at these
wavelengths in any region of sky. We discuss the observation strategy and the
data reduction. The observed source density appears to approach the CAM
confusion limit at 15 micron, and fluctuations in the 6.7 micron sky background
may be identifiable with similar spatial fluctuations in the HDF galaxy counts.
ISO appears to be detecting comparable field galaxy populations to the HDF, and
our data yields strong evidence that future IR missions (such as SIRTF, FIRST
and WIRE) as well as SCUBA and millimetre arrays will easily detect field
galaxies out to comparably high redshifts.Comment: 7 pages, LaTeX (using mn.sty), 9 figures included as GIFs. Gzipped
Postscipt version available from http://artemis.ph.ic.ac.uk/hdf/papers/ps/.
Further information on ISO-HDF project can be found at
http://artemis.ph.ic.ac.uk/hdf
'Dreamersâ, (un)deserving immigrants and generational interdependence
Undocumented young people known as the âDreamersâ have become the embodiment of the âdeserving immigrantâ in US public debates on immigration. Through exploring the narratives of undocumented young organisers in California, this article examines how they came to be framed in this way and the limitations of this as a pathway to social justice. It explores their accounts of organising in the undocumented youth movement to examine how their relationships with their families have influenced their engagement with the Dreamer narrative and its contestation. It was found that the figure of the deserving Dreamer represented an overly individualised account of migrant youth experiences and trajectories. Drawing on a relational understanding of migration and life course pathways, it is argued that undocumented youth are embedded in interdependent intergenerational relationships which affect their experiences and outcomes and therefore need to be recognised in any pathway to social justice
Semiconducting Monolayer Materials as a Tunable Platform for Excitonic Solar Cells
The recent advent of two-dimensional monolayer materials with tunable
optoelectronic properties and high carrier mobility offers renewed
opportunities for efficient, ultra-thin excitonic solar cells alternative to
those based on conjugated polymer and small molecule donors. Using
first-principles density functional theory and many-body calculations, we
demonstrate that monolayers of hexagonal BN and graphene (CBN) combined with
commonly used acceptors such as PCBM fullerene or semiconducting carbon
nanotubes can provide excitonic solar cells with tunable absorber gap,
donor-acceptor interface band alignment, and power conversion efficiency, as
well as novel device architectures. For the case of CBN-PCBM devices, we
predict the limit of power conversion efficiencies to be in the 10 - 20% range
depending on the CBN monolayer structure. Our results demonstrate the
possibility of using monolayer materials in tunable, efficient, polymer-free
thin-film solar cells in which unexplored exciton and carrier transport regimes
are at play.Comment: 7 pages, 5 figure
Diversity of Phytophthora species from natural and semi-natural ecosystems in Portugal, Chile and Vietnam
Diversity of Phytophthora species from natural and semi-natural ecosystems in Portugal, Chile and Vietnam
Theory of Type-II Superconductors with Finite London Penetration Depth
Previous continuum theory of type-II superconductors of various shapes with
and without vortex pinning in an applied magnetic field and with transport
current, is generalized to account for a finite London penetration depth
lambda. This extension is particularly important at low inductions B, where the
transition to the Meissner state is now described correctly, and for films with
thickness comparable to or smaller than lambda. The finite width of the surface
layer with screening currents and the correct dc and ac responses in various
geometries follow naturally from an equation of motion for the current density
in which the integral kernel now accounts for finite lambda. New geometries
considered here are thick and thin strips with applied current, and `washers',
i.e. thin film squares with a slot and central hole as used for SQUIDs.Comment: 14 pages, including 15 high-resolution figure
Diffuse interstitial fibrosis assessed by cardiac magnetic resonance is associated with dispersion of ventricular repolarization in patients with hypertrophic cardiomyopathy
Background Hypertrophic cardiomyopathy (HCM) is characterized by myocyte hypertrophy, disarray, fibrosis, and increased risk for ventricular arrhythmias. Increased QT dispersion has been reported in patients with HCM, but the underlying mechanisms have not been completely elucidated. In this study, we examined the relationship between diffuse interstitial fibrosis, replacement fibrosis, QTc dispersion and ventricular arrhythmias in patients with HCM. We hypothesized that fibrosis would slow impulse propagation and increase dispersion of ventricular repolarization, resulting in increased QTc dispersion on surface electrocardiogram (ECG) and ventricular arrhythmias. Methods ECG and cardiac magnetic resonance (CMR) image analyses were performed retrospectively in 112 patients with a clinical diagnosis of HCM. Replacement fibrosis was assessed by measuring late gadolinium (Gd) enhancement (LGE), using a semi-automated threshold technique. Diffuse interstitial fibrosis was assessed by measuring T1 relaxation times after Gd administration, using the Look?Locker sequence. QTc dispersion was measured digitally in the septal/anterior (V1?V4), inferior (II, III, and aVF), and lateral (I, aVL, V5, and V6) lead groups on surface ECG. Results All patients had evidence of asymmetric septal hypertrophy. LGE was evident in 70 (63%) patients; the median T1 relaxation time was 411±38Êms. An inverse correlation was observed between T1 relaxation time and QTc dispersion in leads V1?V4 (p\u3c 0.001). Patients with HCM who developed sustained ventricular tachycardia had slightly higher probability of increased QTc dispersion in leads V1?V4 (odds ratio, 1.011 [1.004?1.0178, p=0.003). We found no correlation between presence and percentage of LGE and QTc dispersion. Conclusion Diffuse interstitial fibrosis is associated with increased dispersion of ventricular repolarization in leads, reflecting electrical activity in the hypertrophied septum. Interstitial fibrosis combined with ion channel/gap junction remodeling in the septum could lead to inhomogeneity of ventricular refractoriness, resulting in increased QTc dispersion in leads V1?V4
The Galaxy Mass Function up to z=4 in the GOODS-MUSIC sample: into the epoch of formation of massive galaxies
The goal of this work is to measure the evolution of the Galaxy Stellar Mass
Function and of the resulting Stellar Mass Density up to redshift ~4, in order
to study the assembly of massive galaxies in the high redshift Universe. We
have used the GOODS-MUSIC catalog, containing ~3000 Ks-selected galaxies with
multi-wavelength coverage extending from the U band to the Spitzer 8 micron
band, of which 27% have spectroscopic redshifts and the remaining fraction have
accurate photometric redshifts. On this sample we have applied a standard
fitting procedure to measure stellar masses. We compute the Galaxy Stellar Mass
Function and the resulting Stellar Mass Density up to redshift ~4, taking into
proper account the biases and incompleteness effects. Within the well known
trend of global decline of the Stellar Mass Density with redshift, we show that
the decline of the more massive galaxies may be described by an exponential
timescale of ~6 Gyrs up to z~1.5, and proceeds much faster thereafter, with an
exponential timescale of ~0.6 Gyrs. We also show that there is some evidence
for a differential evolution of the Galaxy Stellar Mass Function, with low mass
galaxies evolving faster than more massive ones up to z~1-1.5 and that the
Galaxy Stellar Mass Function remains remarkably flat (i.e. with a slope close
to the local one) up to z~1-1.3. The observed behaviour of the Galaxy Stellar
Mass Function is consistent with a scenario where about 50% of present-day
massive galaxies formed at a vigorous rate in the epoch between redshift 4 and
1.5, followed by a milder evolution until the present-day epoch.Comment: accepted for publication in A&A. Uses aa.cls, 15 pages, 11 figures.
The observed mass functions are available in electronic form at
http://lbc.oa-roma.inaf.it/goods/massfunctio
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