1,568 research outputs found
A performance evaluation of commercial fibrinogen reference preparations and assays for Clauss and PT-derived fibrinogen
The wide availability of fibrinogen estimations based on the prothrombin time (PT-Fg) has caused concern about the variability and clinical utility of fibrinogen assays. In a multi-centre study, we investigated fibrinogen assays using various reagents and analysers, Clauss assays generally gave good agreement, although one reagent gave 15-30% higher values in DIC and thrombolysis. Two commercial reference preparations had much lower potencies than the manufacturers declared, and plasma turbidity influenced parallelism in some Clauss assays, PT-Fg assays gave higher values than Clauss and showed calibrant dependent effects, the degree of disparity correlating with calibrant and test sample turbidity. Analyser and thromboplastin dependent differences were noted. The relationship between Clauss and PT-Fg assays was sigmoid, and the plateau of maximal PT-Fg differed by about 2 g/l between reagents. ELISA and immunonephelometric assays correlated well, but with a high degree of scatter. Antigen levels were higher than Clauss, but slightly lower than PT-Fg assays, which appeared to be influenced by degraded fibrinogen. Clauss assays are generally reproducible between centres, analysers and reagents, but PT-Fg assays are not reliable in clinical settings
Atom-by-Atom Substitution of Mn in GaAs and Visualization of their Hole-Mediated Interactions
The discovery of ferromagnetism in Mn doped GaAs [1] has ignited interest in
the development of semiconductor technologies based on electron spin and has
led to several proof-of-concept spintronic devices [2-4]. A major hurdle for
realistic applications of (Ga,Mn)As, or other dilute magnetic semiconductors,
remains their below room-temperature ferromagnetic transition temperature.
Enhancing ferromagnetism in semiconductors requires understanding the
mechanisms for interaction between magnetic dopants, such as Mn, and
identifying the circumstances in which ferromagnetic interactions are maximized
[5]. Here we report the use of a novel atom-by-atom substitution technique with
the scanning tunnelling microscope (STM) to perform the first controlled atomic
scale study of the interactions between isolated Mn acceptors mediated by the
electronic states of GaAs. High-resolution STM measurements are used to
visualize the GaAs electronic states that participate in the Mn-Mn interaction
and to quantify the interaction strengths as a function of relative position
and orientation. Our experimental findings, which can be explained using
tight-binding model calculations, reveal a strong dependence of ferromagnetic
interaction on crystallographic orientation. This anisotropic interaction can
potentially be exploited by growing oriented Ga1-xMnxAs structures to enhance
the ferromagnetic transition temperature beyond that achieved in randomly doped
samples. Our experimental methods also provide a realistic approach to create
precise arrangements of single spins as coupled quantum bits for memory or
information processing purposes
Sceptical Employees as CSR Ambassadors in Times of Financial Uncertainty
This chapter offers new insights into the understanding of internal (employee) perceptions of organizational corporate social responsibility (CSR) policies and strategies. This study explores the significance of employeesâ involvement and scepticism upon CSR initiatives and focuses on the effects it may have upon word of mouth (WOM) and the development of employeeâorganisation relationships. Desk research introduces the research questions. Data for the research questions were gathered through a self-completion questionnaire distributed in a hardcopy form to the sample. An individualâs level of scepticism and involvement appears to affect the development of a positive effect on employeesâ WOM. Involvement with the domain of the investment may be a central factor affecting relationship building within the organization, and upon generation of positive WOM. The chapter offers a conceptual framework to public relations (PR) and corporate communications practitioners, which may enrich their views and understanding of the use and value of CSR for communication strategies and practices. For-profit organisations are major institutions in todayâs society. CSR is proffered as presenting advantages for (at macro level) society and (micro level) the organization and its employees. Concepts, such as involvement and scepticism, which have not been rigorously examined in PR and corporate communication literature, are addressed. By examining employee perceptions, managers and academic researchers gain insights into the acceptance, appreciation and effectiveness of CSR policies and activities upon the employee stakeholder group. This will affect current and future CSR communication strategies. The knowledge acquired from this chapter may be transferable outside the for-profit sector
XTE J0111.2-7317 : a nebula-embedded X-ray binary in the SMC
The observed characteristics of the nebulosity surrounding the SMC High Mass
X-ray Binary XTE J0111.2-7317 are examined in the context of three possible
nebular types: SNR, bowshock and HII region. Observational evidence is
presented which appears to support the interpretation that the nebulosity
surrounding XTE J0111.2-7317 is an HII region. The source therefore appears to
be a normal SMC Be X-ray binary (BeXRB) embedded in a locally enhanced ISM
which it has photoionised to create an HII region. This is supported by
observations of the X-ray outburst seen with BATSE and RXTE in 1998-1999. It
exhibited characteristics typical of a giant or type II outburst in a BeXRB
including large spin-up rates, Lx~10E38 erg/sq.cm-s, and a correlation between
spin-up rate and pulsed flux. However, the temporal profile of the outburst was
unusual, consisting of two similar intensity peaks, with the first peak of
shorter duration than the second.Comment: Accepted for publication by MNRA
Enhanced spatial resolution through DFT rederivations of X-ray phase retrieval algorithms
Propagation-based phase-contrast imaging, used in conjunction with the phase
retrieval algorithm based on the Transport-of-Intensity Equation (TIE) (Paganin
et al., 2002), is commonly used to improve the sensitivity of X-ray imaging.
Recently, a `Generalised Paganin Method' algorithm was published to correct the
tendency of the TIE algorithm to over-blur images. The article, Paganin et al.
2020, provided a derivation of the new method and demonstrated a difference in
the level of blurring applied by each algorithm. In this manuscript, we
quantify the spatial resolution improvement and describe the optimal
experimental conditions to observe this improvement. We link the effectiveness
of the spatial resolution improvement to the imaging point spread function
(PSF), incorporating the PSF to compare the blurring applied by each algorithm.
We then validate this model through measurements of spatial resolution in
experimental data imaging plastic phantoms and biological tissue, using
detectors with different PSFs. By analysing edge-spread functions in CT data
captured with indirect detectors with PSFs of several pixels in extent, we show
negligible spatial resolution improvement when using the generalised Paganin
method. However, a clear improvement in spatial resolution, up to 17%, was
observed with direct detectors having PSFs of approximately one pixel in
extent. Additionally, we demonstrate clear visual improvement in resolution in
CT slices of rat lungs. Finally, we demonstrate the versatility of this
improvement by generalising other phase retrieval algorithms, namely for
multi-material samples and for spectral decomposition using propagation-based
phase contrast, and experimentally verify improvements in spatial resolution
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