240 research outputs found
Investigation of iterative image reconstruction in three-dimensional optoacoustic tomography
Iterative image reconstruction algorithms for optoacoustic tomography (OAT),
also known as photoacoustic tomography, have the ability to improve image
quality over analytic algorithms due to their ability to incorporate accurate
models of the imaging physics, instrument response, and measurement noise.
However, to date, there have been few reported attempts to employ advanced
iterative image reconstruction algorithms for improving image quality in
three-dimensional (3D) OAT. In this work, we implement and investigate two
iterative image reconstruction methods for use with a 3D OAT small animal
imager: namely, a penalized least-squares (PLS) method employing a quadratic
smoothness penalty and a PLS method employing a total variation norm penalty.
The reconstruction algorithms employ accurate models of the ultrasonic
transducer impulse responses. Experimental data sets are employed to compare
the performances of the iterative reconstruction algorithms to that of a 3D
filtered backprojection (FBP) algorithm. By use of quantitative measures of
image quality, we demonstrate that the iterative reconstruction algorithms can
mitigate image artifacts and preserve spatial resolution more effectively than
FBP algorithms. These features suggest that the use of advanced image
reconstruction algorithms can improve the effectiveness of 3D OAT while
reducing the amount of data required for biomedical applications
Doping a semiconductor to create an unconventional metal
Landau Fermi liquid theory, with its pivotal assertion that electrons in
metals can be simply understood as independent particles with effective masses
replacing the free electron mass, has been astonishingly successful. This is
true despite the Coulomb interactions an electron experiences from the host
crystal lattice, its defects, and the other ~1022/cm3 electrons. An important
extension to the theory accounts for the behaviour of doped semiconductors1,2.
Because little in the vast literature on materials contradicts Fermi liquid
theory and its extensions, exceptions have attracted great attention, and they
include the high temperature superconductors3, silicon-based field effect
transistors which host two-dimensional metals4, and certain rare earth
compounds at the threshold of magnetism5-8. The origin of the non-Fermi liquid
behaviour in all of these systems remains controversial. Here we report that an
entirely different and exceedingly simple class of materials - doped small gap
semiconductors near a metal-insulator transition - can also display a non-Fermi
liquid state. Remarkably, a modest magnetic field functions as a switch which
restores the ordinary disordered Fermi liquid. Our data suggest that we have
finally found a physical realization of the only mathematically rigourous route
to a non-Fermi liquid, namely the 'undercompensated Kondo effect', where there
are too few mobile electrons to compensate for the spins of unpaired electrons
localized on impurity atoms9-12.Comment: 17 pages 4 figures supplemental information included with 2 figure
Interesting magnetic properties of FeCoSi alloys
Solid solution between nonmagnetic narrow gap semiconductor FeSi and
diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with
long-range helical magnetic ordering, for a wide range of intermediate
concentration. We report various interesting magnetic properties of these
alloys, including low temperature re-entrant spin-glass like behaviour and a
novel inverted magnetic hysteresis loop. Role of Dzyaloshinski-Moriya
interaction in the magnetic response of these non-centrosymmetric alloys is
discussed.Comment: 11 pages and 3 figure
A multi-start heuristic for multiplicative depth minimization of boolean circuits
In this work we propose a multi-start heuristic which aims at minimizing the multiplicative depth of boolean circuits. The multiplicative depth objective is encountered in the field of homomorphic encryption where ciphertext size depends on the number of consecutive multiplications. The heuristic is based on rewrite operators for multiplicative depth-2 paths. Even if the proposed rewrite operators are simple and easy to understand the experimental results show that they are rather powerful. The multiplicative depth of the benchmarked circuits was hugely improved. In average the obtained multiplicative depths were lower by more than 3 times than the initial ones. The proposed rewrite operators are not limited to boolean circuits and can also be used for arithmetic circuits
The celebrity entrepreneur on television: profile, politics and power
This article examines the rise of the âcelebrity entrepreneurâ on television through the emergence of the âbusiness entertainment formatâ and considers the ways in which regular television exposure can be converted into political influence. Within television studies there has been a preoccupation in recent years with how lifestyle and reality formats work to transform âordinaryâ people into celebrities. As a result, the contribution of vocationally skilled business professionals to factual entertainment programming has gone almost unnoticed. This article draws on interviews with key media industry professionals and begins by looking at the construction of entrepreneurs as different types of television personalities and how discourses of work, skill and knowledge function in business shows. It then outlines how entrepreneurs can utilize their newly acquired televisual skills to cultivate a wider media profile and secure various forms of political access and influence. Integral to this is the centrality of public relations and media management agencies in shaping media discourses and developing the individual as a âbrand identityâ that can be used to endorse a range of products or ideas. This has led to policy makers and politicians attempting to mobilize the media profile of celebrity entrepreneurs to reach out and connect with the public on business and enterprise-related issues
Electrical behaviour, characteristics and properties of anodic aluminium oxide films coloured by nickel electrodeposition
Porous anodic films on 1050 aluminium substrate were coloured by AC electrodeposition of nickel. Several experiments were performed at different deposition voltages and nickel concentrations in the electrolyte in order to correlate the applied electrical power to the electrical behaviour, as well as the characteristics and properties of the coatings. The content of nickel inside the coatings reached 1.67 g/m2, depending on the experimental conditions. According to the applied AC voltage in comparison with the threshold voltage Ut, the coating either acted only as a capacitor when U\Ut and, when U[Ut, the behaviour during the anodic and cathodic parts of the power sine wave was different. In particular, due to the semi-conducting characteristics of the barrier layer, additional oxidation of the aluminium substrate occurred during the anodic part of the electrical signal, whilst metal deposition (and solvent reduction) occurred during the cathodic part; these mechanisms correspond to the blocked and pass directions of the barrier layer/electrolyte junction, respectively
The impact of marketisation on postgraduate career preparedness in a high skills economy
This study focuses on the consequences for high skills development of the erosion of the once clear demarcation between higher education and business. It contributes to the broader debate about the relevance of higher education for thewell-being of the society of the future. The research explores the effects of marketisation on the postgraduate curriculum and studentsâ preparedness for careers in public relations and marketing communications. Interviews with lecturers and students in two universities in the UK and Australia indicate that a tension exists between academic rigour and corporate relevancy. The consequences are a diminution of academic attachment to critique and wider social/cultural engagement, with a resulting impoverishment of studentsâ creative abilities and critical consciences. Subsequently, graduates of public relations and marketing communications, and to some extent those from other profession-related disciplines, are insufficiently prepared for careers as knowledge workers in a future high-skills economy
Poland's 2011 Online Election Campaign: New Tools, New Professionalism, New Ways to Win Votes
This article analyzes the use of the online environment within the context of the Polish parliamentary election of 2011. Using traditional methods of content analysis, we find that parties tend to adhere to a professionalized model of campaigning, and adapting online tools to suit the objectives of the campaign. There also appears to be a recognition that their most likely visitors to these online presences would be converts, and so they attempt to mobilize supporters rather than convert browsers. New parties and candidates are more likely to target browsers, with the latter offering a more personalized experience to online visitors. Importantly, when analyzing the outcome of the contest, we find that being online matters for candidates when controlling for all other variables. Equally, the reach the candidate has, which may well influence their vote share, is dependent on offering a more personalized, representational image and having a frequently updated online presence that should encourage repeat visits. Cumulatively, we suggest the future of online campaigning must not only focus on having a presence, but on using it in a way that appeals to a range of visitors, encouraging repeat visits, and that this strategy could have a positive impact on election outcomes. © Taylor & Francis Group, LLC
Marketing and the cultural production of celebrity in the era of media convergence
Celebrity endorsement research in the marketing literature has been over-reliant on an exogenous notion of celebrity as something produced outside of the marketing system, from which meanings can be transferred to brands within the marketing system. In fact, marketing has been deeply implicated in the constitution of celebrity since the dawn of Western consumer culture in the early part of the twentieth century. In the era of media convergence, there is a pressing need for researchers in marketing to re-evaluate the meta-assumptions around celebrity and its relation to marketing in the light of marketingâs culturally constitutive role
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