16,638 research outputs found
The quarter-point quadratic isoparametric element as a singular element for crack problems
The quadratic isoparametric elements which embody the inverse square root singularity are used for calculating the stress intensity factors at tips of cracks. The strain singularity at a point or an edge is obtained in a simple manner by placing the mid-side nodes at quarter points in the vicinity of the crack tip or an edge. These elements are implemented in NASTRAN as dummy elements. The method eliminates the use of special crack tip elements and in addition, these elements satisfy the constant strain and rigid body modes required for convergence
Patient and health care professional decision-making to commence and withdraw from renal dialysis: A systematic review of qualitative research
Background and objectives. To ensure decisions to start and stop dialysis in end stage kidney disease are shared, the factors that affect patients and healthcare professionals in making such decisions need to be understood. This systematic review aims to explore how and why different factors mediate the choices about dialysis treatment. Design, setting, participants, and measurements. Medline, Embase, CINAHL and PsychINFO were searched for qualitative studies of factors that affect patients’ and/or healthcare professionals’ decisions to commence or withdraw from dialysis. A thematic synthesis was conducted. Results. Of 494 articles screened, 12 studies (conducted: 1985-2014) were included. These involved 206 predominantly haemodialysis patients and 64 healthcare professionals (age range: patients 26-93; professionals 26-61 years). (i) Commencing dialysis: patients based their choice on ‘gut-instinct’ as well as deliberating the impact of treatment on quality-of-life and survival. How individuals coped with decision-making was influential, some tried to take control of the problem of progressive renal failure, whilst others focussed on controlling their emotions. Healthcare professionals weighed-up biomedical factors and were led by an instinct to prolong life. Both patients and healthcare professionals described feeling powerless. (ii) Dialysis withdrawal: Only after prolonged periods of time on dialysis, were the realities of life on dialysis fully appreciated and past choice questioned. By this stage however patients were physically treatment dependent. Similar to commencing dialysis, individuals coped with treatment withdrawal in a problem or emotion-controlling way. Families struggled to differentiate choosing versus allowing death. Healthcare teams avoided and queried discussions regarding dialysis withdrawal. Patients however missed the dialogue they experienced during pre-dialysis education. Conclusions. Decision-making in end stage kidney disease is complex, dynamic, and evolves over time and towards death. The factors at work are multi-faceted and operate differently for patients and health professionals. More training and research on open-communication and shared decision-making is needed
Comparing time series with machine learning-based prediction approaches for violation management in cloud SLAs
© 2018 In cloud computing, service level agreements (SLAs) are legal agreements between a service provider and consumer that contain a list of obligations and commitments which need to be satisfied by both parties during the transaction. From a service provider's perspective, a violation of such a commitment leads to penalties in terms of money and reputation and thus has to be effectively managed. In the literature, this problem has been studied under the domain of cloud service management. One aspect required to manage cloud services after the formation of SLAs is to predict the future Quality of Service (QoS) of cloud parameters to ascertain if they lead to violations. Various approaches in the literature perform this task using different prediction approaches however none of them study the accuracy of each. However, it is important to do this as the results of each prediction approach vary according to the pattern of the input data and selecting an incorrect choice of a prediction algorithm could lead to service violation and penalties. In this paper, we test and report the accuracy of time series and machine learning-based prediction approaches. In each category, we test many different techniques and rank them according to their order of accuracy in predicting future QoS. Our analysis helps the cloud service provider to choose an appropriate prediction approach (whether time series or machine learning based) and further to utilize the best method depending on input data patterns to obtain an accurate prediction result and better manage their SLAs to avoid violation penalties
Fault-tolerance thresholds for the surface code with fabrication errors
The construction of topological error correction codes requires the ability
to fabricate a lattice of physical qubits embedded on a manifold with a
non-trivial topology such that the quantum information is encoded in the global
degrees of freedom (i.e. the topology) of the manifold. However, the
manufacturing of large-scale topological devices will undoubtedly suffer from
fabrication errors---permanent faulty components such as missing physical
qubits or failed entangling gates---introducing permanent defects into the
topology of the lattice and hence significantly reducing the distance of the
code and the quality of the encoded logical qubits. In this work we investigate
how fabrication errors affect the performance of topological codes, using the
surface code as the testbed. A known approach to mitigate defective lattices
involves the use of primitive SWAP gates in a long sequence of syndrome
extraction circuits. Instead, we show that in the presence of fabrication
errors the syndrome can be determined using the supercheck operator approach
and the outcome of the defective gauge stabilizer generators without any
additional computational overhead or the use of SWAP gates. We report numerical
fault-tolerance thresholds in the presence of both qubit fabrication and gate
fabrication errors using a circuit-based noise model and the minimum-weight
perfect matching decoder. Our numerical analysis is most applicable to 2D
chip-based technologies, but the techniques presented here can be readily
extended to other topological architectures. We find that in the presence of 8%
qubit fabrication errors, the surface code can still tolerate a computational
error rate of up to 0.1%.Comment: 10 pages, 15 figure
Vulnerability of Corals to Seawater Warming
Coral reefs are the most diverse marine habitat, which support an estimated 1 million species globally. They are highly sensitive to climatic influences and are among the most sensitive of all ecosystems to temperature changes, exhibiting the phenomenon known as coral bleaching when stressed by higher than normal sea temperatures. Reef-building corals are highly dependent on a symbiotic relationship with microscopic algae (type of dinoflagellate known as zooxanthellae), which live within the coral tissues
Multi-wavelength observing of a forming solar-like star
V2129 Oph is a 1.35 solar mass classical T Tauri star, known to possess a
strong and complex magnetic field. By extrapolating from an observationally
derived magnetic surface map, obtained through Zeeman-Doppler imaging, models
of V2129 Oph's corona have been constructed, and used to make predictions
regarding the global X-ray emission measure, the amount of modulation of X-ray
emission, and the density of accretion shocks. In late June 2009 we will under
take an ambitious multi-wavelength, multi-observing site, and near
contemporaneous campaign, combining spectroscopic optical, nIR, UV, X-ray,
spectropolarimetric and photometric monitoring. This will allow the validity of
the 3D field topologies derived via field extrapolation to be determined.Comment: 4 pages, proceedings of the 3rd MSSL workshop on High Resolution
X-ray Spectroscopy: towards IX
Association of Urinary Vitamin D-binding Protein and Megalin as Biomarkers for Diabetic Nephropathy in Type 2 Diabetes Mellitus in Qatari Patients
Abstract
Background: Nephropathy is a common complication of type 2 diabetes mellitus (T2DM). Previous studies
revealed that T2DM patients with nephropathy have higher concentrations of urinary Vitamin D Binding Protein
(VDBP) that carries vitamin D to the target tissues, and megalin that mediates endocytosis in the proximal tubule
than those who are healthy.
Methodology: 196 urine samples with their blood data were obtained from Qatar Biobank, of which 21 samples
were measured for VDBP and megalin using enzyme-linked immunosorbent assay (ELISA). They were divided intothree groups; group 1 (control group with eGFR ≥ 90 mL/min/1.73 m²), group 2 (T2DM patients with eGFR ≥ 90 mL/min/1.73 m²) and group 3; (T2DM patients with eGFR < 90 mL/min/1.73 m²).
Results: Urinary VDBP and Megalin levels were non-significantly elevated in T2DM patients with DN (P=0.198)
and (P=0.293) respectively. Moreover, a weak negative correlation was observed between the urinary VDBP and
Megalin levels with eGFR (r=-0.326, P=0.149) and (r=-0.315, P=0.165) respectively.
Conclusion: Previous studies revealed that uVDBP and Megalin are potential biomarkers for DN in T2DM
patients. However, the current study reveals that urinary VDBP and megalin levels were non-significantly elevated in T2DM patients with DN. Furthermore, eGFR showed a weak negative correlation with urinary VDBP and megalin levels. However, it is suggested that these results could be due to some limitations. Further tests should be performed on larger sample size to confirm the association of Megalin and VDBP in T2DM nephropathy
Discovery of new magnetic early-B stars within the MiMeS HARPSpol survey
To understand the origin of the magnetic fields in massive stars as well as
their impact on stellar internal structure, evolution, and circumstellar
environment, within the MiMeS project, we searched for magnetic objects among a
large sample of massive stars, and build a sub-sample for in-depth follow-up
studies required to test the models and theories of fossil field origins,
magnetic wind confinement and magnetospheric properties, and magnetic star
evolution.
We obtained high-resolution spectropolarimetric observations of a large
number of OB stars thanks to three large programs that have been allocated on
the high-resolution spectropolarimeters ESPaDOnS, Narval, and the polarimetric
module HARPSpol of the HARPS spectrograph. We report here on the methods and
first analysis of the HARPSpol magnetic detections. We identified the magnetic
stars using a multi-line analysis technique. Then, when possible, we monitored
the new discoveries to derive their rotation periods, which are critical for
follow-up and magnetic mapping studies. We also performed a first-look analysis
of their spectra and identified obvious spectral anomalies (e.g., abundance
peculiarities, Halpha emission), which are also of interest for future studies.
In this paper, we focus on eight of the 11 stars in which we discovered or
confirmed a magnetic field from the HARPSpol LP sample (the remaining three
were published in a previous paper). Seven of the stars were detected in
early-type Bp stars, while the last star was detected in the Ap companion of a
normal early B-type star. We report obvious spectral and multiplicity
properties, as well as our measurements of their longitudinal field strengths,
and their rotation periods when we are able to derive them. We also discuss the
presence or absence of Halpha emission with respect to the theory of
centrifugally-supported magnetospheres. (Abriged)Comment: 19 pages, 8 figures, accepted for publication in A&
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