1,303 research outputs found
A Modular Approach to the Development of Interactive Augmented Reality Applications.
Augmented reality (AR) technologies are becoming increasingly popular as a result of the increase in the power of mobile computing devices. Emerging AR applications have the potential to have an enormous impact on industries such as education, healthcare, research, training and entertainment. There are currently a number of augmented reality toolkits and libraries available for the development of these applications; however, there is currently no standard tool for development. In this thesis we propose a modular approach to the organization and development of AR systems in order to enable the creation novel AR experiences. We also investigate the incorporation of the framework that resulted from our approach into game engines to enable the creation and visualization of immersive virtual reality experiences. We address issues in the development process of AR systems and provide a solution for reducing the time, cost and barrier of entry for development while simultaneously providing a framework in which researchers can test and apply advanced augmented reality technologies
Generation and Distribution of Quantum Oblivious Keys for Secure Multiparty Computation
The oblivious transfer primitive is sufficient to implement secure multiparty
computation. However, secure multiparty computation based only on classical
cryptography is severely limited by the security and efficiency of the
oblivious transfer implementation. We present a method to efficiently and
securely generate and distribute oblivious keys by exchanging qubits and by
performing commitments using classical hash functions. With the presented
hybrid approach, quantum and classical, we obtain a practical and high-speed
oblivious transfer protocol, secure even against quantum computer attacks. The
oblivious distributed keys allow implementing a fast and secure oblivious
transfer protocol, which can pave the way for the widespread of applications
based on secure multiparty computation.Comment: 11 pages, 5 figure
A Numerical Study of Brown Dwarf Formation via Encounters of Protostellar Disks
The formation of brown dwarfs (BDs) due to the fragmentation of proto-stellar
disks undergoing pairwise encounters was investigated. High resolution allowed
the use of realistic initial disk models where both the vertical structure and
the local Jeans mass were resolved. The results show that objects with masses
ranging from giant planets to low mass stars can form during such encounters
from initially stable disks. The parameter space of initial spin-orbit
orientations and the azimuthal angles for each disk was explored. An upper
limit on the initial Toomre Q value of ~2 was found for fragmentation to occur.
Depending on the initial configuration, shocks, tidal-tail structures and mass
inflows were responsible for the condensation of disk gas. Retrograde disks
were generally more likely to fragment. When the interaction timescale was
significantly shorter than the disks' dynamical timescales, the proto-stellar
disks tended to be truncated without forming objects.
The newly-formed objects had masses ranging from 0.9 to 127 Jupiter masses,
with the majority in the BD regime. They often resided in star-BD multiples and
in some cases also formed hierarchical orbiting systems. Most of them had large
angular momenta and highly flattened, disk-like shapes. The objects had radii
ranging from 0.1 to 10 AU. The disk gas was assumed to be locally isothermal,
appropriate for the short cooling times in extended proto-stellar disks, but
not for condensed objects. An additional case with explicit cooling that
reduced to zero for optically thick gas was simulated to test the extremes of
cooling effectiveness and it was still possible to form objects in this case.
Detailed radiative transfer is expected to lengthen the internal evolution
timescale for these objects, but not to alter our basic results.Comment: 18 pages, 12 figures and 2 tables. Accepted for publication in MNRA
Human umbilical cord blood-derived mononuclear cells improve murine ventricular function upon intramyocardial delivery in right ventricular chronic pressure overload
Stem cell therapy has emerged as potential therapeutic strategy for damaged heart muscles. Umbilical cord blood (UCB) cells are the most prevalent stem cell source available, yet have not been fully tested in cardiac regeneration. Herein, studies were performed to evaluate the cardiovascular safety and beneficial effect of mononuclear cells (MNCs) isolated from human umbilical cord blood upon intramyocardial delivery in a murine model of right ventricle (RV) heart failure due to pressure overload. UCB-derived MNCs were delivered into the myocardium of a diseased RV cardiac model. Pulmonary artery banding (PAB) was used to produce pressure overload in athymic nude mice that were then injected intramyocardially with UCB-MNCs (0.4 × 10^6 cells/heart). Cardiac functions were then monitored by telemetry, echocardiography, magnetic resonance imaging (MRI) and pathologic analysis of heart samples to determine the ability for cell-based repair. The cardio-toxicity studies provided evidence that UCB cell transplantation has a safe therapeutic window between 0.4 to 0.8 million cells/heart without altering QT or ST-segments or the morphology of electrocardiograph waves. The PAB cohort demonstrated significant changes in RV chamber dilation and functional defects consistent with severe pressure overload. Using cardiac MRI analysis, UCB-MNC transplantation in the setting of PAB demonstrated an improvement in RV structure and function in this surgical mouse model. The RV volume load in PAB-only mice was 24.09 ± 3.9 compared to 11.05 ± 2.09 in the cell group (mm 3, P -value <0.005). The analysis of pathogenic gene expression (BNP, ANP, Acta1, Myh7) in the cell-transplanted group showed a significant reversal with respect to the diseased PAB mice with a robust increase in cardiac progenitor gene expression such as GATA4, Kdr, Mef2c and Nkx2.5. Histological analysis indicated significant fibrosis in the RV in response to PAB that was reduced following UCB-MNC's transplantation along with concomitant increased Ki-67 expression and CD31 positive vessels as a marker of angiogenesis within the myocardium. These findings indicate that human UCB-derived MNCs promote an adaptive regenerative response in the right ventricle upon intramyocardial transplantation in the setting of chronic pressure overload heart failure
Quantum computing implementations with neutral particles
We review quantum information processing with cold neutral particles, that
is, atoms or polar molecules. First, we analyze the best suited degrees of
freedom of these particles for storing quantum information, and then we discuss
both single- and two-qubit gate implementations. We focus our discussion mainly
on collisional quantum gates, which are best suited for atom-chip-like devices,
as well as on gate proposals conceived for optical lattices. Additionally, we
analyze schemes both for cold atoms confined in optical cavities and hybrid
approaches to entanglement generation, and we show how optimal control theory
might be a powerful tool to enhance the speed up of the gate operations as well
as to achieve high fidelities required for fault tolerant quantum computation.Comment: 19 pages, 12 figures; From the issue entitled "Special Issue on
Neutral Particles
Appointing Women to Boards: Is There a Cultural Bias?
Companies that are serious about corporate governance and business ethics are turning their attention to gender diversity at the most senior levels of business (Institute of Business Ethics, Business Ethics Briefing 21:1, 2011). Board gender diversity has been the subject of several studies carried out by international organizations such as Catalyst (Increasing gender diversity on boards: Current index of formal approaches, 2012), the World Economic Forum (Hausmann et al., The global gender gap report, 2010), and the European Board Diversity Analysis (Is it getting easier to find women on European boards? 2010). They all lead to reports confirming the overall relatively low proportion of women on boards and the slow pace at which more women are being appointed. Furthermore, the proportion of women on corporate boards varies much across countries. Based on institutional theory, this study hypothesizes and tests whether this variation can be attributed to differences in cultural settings across countries. Our analysis of the representation of women on boards for 32 countries during 2010 reveals that two cultural characteristics are indeed associated with the observed differences. We use the cultural dimensions proposed by Hofstede (Culture’s consequences: International differences in work-related values, 1980) to measure this construct. Results show that countries which have the greatest tolerance for inequalities in the distribution of power and those that tend to value the role of men generally exhibit lower representations of women on boards
Cardiogenic Induction of Pluripotent Stem Cells Streamlined Through a Conserved SDF-1/VEGF/BMP2 Integrated Network
BACKGROUND: Pluripotent stem cells produce tissue-specific lineages through programmed acquisition of sequential gene expression patterns that function as a blueprint for organ formation. As embryonic stem cells respond concomitantly to diverse signaling pathways during differentiation, extraction of a pro-cardiogenic network would offer a roadmap to streamline cardiac progenitor output. METHODS AND RESULTS: To resolve gene ontology priorities within precursor transcriptomes, cardiogenic subpopulations were here generated according to either growth factor guidance or stage-specific biomarker sorting. Innate expression profiles were independently delineated through unbiased systems biology mapping, and cross-referenced to filter transcriptional noise unmasking a conserved progenitor motif (55 up- and 233 down-regulated genes). The streamlined pool of 288 genes organized into a core biological network that prioritized the "Cardiovascular Development" function. Recursive in silico deconvolution of the cardiogenic neighborhood and associated canonical signaling pathways identified a combination of integrated axes, CXCR4/SDF-1, Flk-1/VEGF and BMP2r/BMP2, predicted to synchronize cardiac specification. In vitro targeting of the resolved triad in embryoid bodies accelerated expression of Nkx2.5, Mef2C and cardiac-MHC, enhanced beating activity, and augmented cardiogenic yield. CONCLUSIONS: Transcriptome-wide dissection of a conserved progenitor profile thus revealed functional highways that coordinate cardiogenic maturation from a pluripotent ground state. Validating the bioinformatics algorithm established a strategy to rationally modulate cell fate, and optimize stem cell-derived cardiogenesis
Quantum state preparation and macroscopic entanglement in gravitational-wave detectors
Long-baseline laser-interferometer gravitational-wave detectors are operating
at a factor of 10 (in amplitude) above the standard quantum limit (SQL) within
a broad frequency band. Such a low classical noise budget has already allowed
the creation of a controlled 2.7 kg macroscopic oscillator with an effective
eigenfrequency of 150 Hz and an occupation number of 200. This result, along
with the prospect for further improvements, heralds the new possibility of
experimentally probing macroscopic quantum mechanics (MQM) - quantum mechanical
behavior of objects in the realm of everyday experience - using
gravitational-wave detectors. In this paper, we provide the mathematical
foundation for the first step of a MQM experiment: the preparation of a
macroscopic test mass into a nearly minimum-Heisenberg-limited Gaussian quantum
state, which is possible if the interferometer's classical noise beats the SQL
in a broad frequency band. Our formalism, based on Wiener filtering, allows a
straightforward conversion from the classical noise budget of a laser
interferometer, in terms of noise spectra, into the strategy for quantum state
preparation, and the quality of the prepared state. Using this formalism, we
consider how Gaussian entanglement can be built among two macroscopic test
masses, and the performance of the planned Advanced LIGO interferometers in
quantum-state preparation
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure
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