633 research outputs found
The Economics of Healthcare Rationing
This article examines the economics of healthcare rationing. We begin with an overview of the various dimensions across which healthcare rationing operates, or at least has the potential to operate, in the first place. We then describe the types of economic analyses used in healthcare rationing decision-making, with particular reference to cost-benefit analysis and cost-effectiveness analysis. We also discuss healthcare rationing in practice, such as how economic analyses inform decisions regarding which services to cover, and conclude by discussing various practical and conceptual challenges that may arise with economic analyses and that span both economics and ethics
Identification of Decoherence-Free Subspaces Without Quantum Process Tomography
Characterizing a quantum process is the critical first step towards applying
such a process in a quantum information protocol. Full process characterization
is known to be extremely resource-intensive, motivating the search for more
efficient ways to extract salient information about the process. An example is
the identification of "decoherence-free subspaces", in which computation or
communications may be carried out, immune to the principal sources of
decoherence in the system. Here we propose and demonstrate a protocol which
enables one to directly identify a DFS without carrying out a full
reconstruction. Our protocol offers an up-to-quadratic speedup over standard
process tomography. In this paper, we experimentally identify the DFS of a
two-qubit process with 32 measurements rather than the usual 256, characterize
the robustness and efficiency of the protocol, and discuss its extension to
higher-dimensional systems.Comment: 6 pages, 5 figure
Adaptive quantum state tomography improves accuracy quadratically
We introduce a simple protocol for adaptive quantum state tomography, which
reduces the worst-case infidelity between the estimate and the true state from
to . It uses a single adaptation step and just one
extra measurement setting. In a linear optical qubit experiment, we demonstrate
a full order of magnitude reduction in infidelity (from to ) for
a modest number of samples ().Comment: 8 pages, 7 figure
Scalable Spatial Super-Resolution using Entangled Photons
N00N states -- maximally path-entangled states of N photons -- exhibit
spatial interference patterns sharper than any classical interference pattern.
This is known as super-resolution. However, even with perfectly efficient
number-resolving detectors, the detection efficiency of all previously
demonstrated methods to measure such interference decreases exponentially with
the number of photons in the N00N state, often leading to the conclusion that
N00N states are unsuitable for spatial measurements. Here, we create spatial
super-resolution fringes with two-, three-, and four-photon N00N states, and
demonstrate a scalable implementation of the so-called ``optical centroid
measurement'' which provides an in-principle perfect detection efficiency.
Moreover, we compare the N00N-state interference to the corresponding classical
super-resolution interference. Although both provide the same increase in
spatial frequency, the visibility of the classical fringes decreases
exponentially with the number of detected photons, while the visibility of our
experimentally measured N00N-state super-resolution fringes remains
approximately constant with N. Our implementation of the optical centroid
measurement is a scalable method to measure high photon-number quantum
interference, an essential step forward for quantum-enhanced measurements,
overcoming what was believed to be a fundamental challenge to quantum
metrology
Acid-Labile Traceless Click Linker for Protein Transduction
Intracellular delivery of active proteins presents an interesting approach in research and therapy. We created a protein transduction shuttle based on a new traceless click linker that combines the advantages of click reactions with implementation of reversible pH-sensitive bonds. The azidomethyl-methylmaleic anhydride (AzMMMan) linker was found compatible with different click chemistries, demonstrated in bioreversible protein modification with dyes, polyethylene glycol, or a transduction carrier. Linkages were stable at physiological pH but reversible at the mild acidic pH of endosomes or lysosomes. We show that pH-reversible attachment of a defined endosome-destabilizing three-arm oligo(ethane amino)amide carrier generates an effective shuttle for protein delivery. The cargo protein nlsEGFP, when coupled via the traceless AzMMMan linker, experiences efficient cellular uptake and endosomal escape into the cytosol, followed by import into the nucleus. In contrast, irreversible linkage to the same shuttle hampers nuclear delivery of nlsEGFP which after uptake remains trapped in the cytosol. Successful intracellular delivery of bioactive ß-galactosidase as a model enzyme was also demonstrated using the pH-controlled shuttle system
On the correct formula for the lifetime broadened superconducting density of states
We argue that the well known Dynes formula [Dynes R C {\it et al.} 1978 {\it
Phys. Rev. Lett.} {\bf 41} 1509] for the superconducting quasiparticle density
of states, which tries to incorporate the lifetime broadening in an approximate
way, cannot be justified microscopically for conventional superconductors.
Instead, we propose a new simple formula in which the energy gap has a finite
imaginary part and the quasiparticle energy is real. We prove that
in the quasiparticle approximation 2 gives the quasiparticle decay
rate at the gap edge for conventional superconductors. This conclusion does not
depend on the nature of interactions that cause the quasiparticle decay. The
new formula is tested on the case of a strong coupling superconductor
PbBi and an excellent agreement with theoretical predictions is
obtained. While both the Dynes formula and the one proposed in this work give
good fits and fit parameters for PbBi, only the latter formula
can be justified microscopically.Comment: 6 pages, 4 figure
Shedding light on sporopollenin chemistry, with reference to UV reconstructions
Sporopollenin, which forms the outer wall of pollen and spores, contains a chemical signature of ultraviolet-B flux via concentrations of UV-B absorbing compounds (UACs), providing a proxy for reconstructing UV irradiance through time. Although Fourier transform infrared (FTIR) spectroscopy provides an efficient means of measuring UAC concentrations, nitrogen-containing compounds have the potential to bias the aromatic and hydroxyl bands used to quantify and standardise UAC abundances. Here, we explore the presence and possible influence of nitrogen in UV reconstruction via an FTIR study of Lycopodium spores from a natural shading gradient. We show that the UV-sensitive aromatic peak at 1510 cm− 1 is clearly distinguishable from the amide II peak at 1550 cm− 1, and the decrease in aromatic content with increased shading can be reconstructed using standardisation approaches that do not rely on the 3300 cm− 1 hydroxyl band. Isolation of the sporopollenin results in the loss of nitrogen-related peaks from the FTIR spectra, while the aromatic gradient remains. This confirms the lack of nitrogen in sporopollenin and its limited potential for impacting on palaeo-UV reconstructions. FTIR is therefore an appropriate tool for quantifying UACs in spores and pollen, and information on UV flux should be obtainable from fossil or processed samples
Personalized Optical Designs and Manipulating Optics: Applications on the Anterior Segment of the Eye
The image-forming properties of the eye can be described in terms of wave aberration. Understanding the link between aberrations and the anterior segment geometry is therefore of crucial importance for (i) comprehending how the eye works, (ii) modelling the optics of individual eyes, (iii) optimizing optical solutions, or (iv) designing surgical strategies. The eye has many innate adaptations that minimize optical aberrations. In most normal young eyes, the magnitude of aberrations of the cornea is significantly larger than for the whole eye, indicating a significant role of the crystalline lens in compensating corneal aberrations. However, due to geometrical and structural changes, this ocular compensation gets disturbed in different anterior segment conditions, such as keratoconus, presbyopia, or cataract. Keratoconus progressively degrades the corneal shape and, consequently, vision in the adolescence, with a prevalence of 0.05% in the general population. Meanwhile, presbyopia and cataract are conditions related to aging that affect the structure of the crystalline lens, one referring to a loss in accommodative amplitude (presbyopia) and the other to a progressive loss of transparency (cataract). Presbyopia affects 100% of the population older than 45¿years of age, ..
Implementation of an outdoor smoke-free policy at sports clubs: Critical situations and determinants influencing implementation
Background Outdoor smoke-free policies (SFPs) at sports clubs have significant potential to reduce adolescent smoking. However, the realization of this potential may be strongly dependent on how these policies are implemented in practice. The aim of this study is to explore the perceptions of key stakeholders at different sports clubs in the Netherlands concerning how outdoor SFPs are implemented in practice and which determinants influence implementation. Methods Semi-structured interviews were held with 46 key stakeholders at eight Dutch sports clubs (i.e., field hockey, soccer, tennis, korfball) with an outdoor SFP. A thematic approach was used for the analysis of the transcripts. Results Overall, respondents perceived the implementation of an outdoor SFP at sports clubs as feasible. The SFP is often enforced, people who smoke react positively when they are approached, the SFP has led to less (visible) smoking at the venue, and a nonsmoking norm is reinforced. However, we identified three ‘critical situations’ in which implementation is less than optimal: 1) when children are not present at the sports club, 2) when alcohol is involved, and 3) when people who smoke relocate to the entrance of the sports club. Several determinants influenced implementation in those critical situations: 1) determinants related to individual smokers and club members (i.e., support, communication towards people who smoke), 2) determinants related to the SFP itself (i.e., clarity of the policy), 3) determinants related to the sports club (i.e., communication of the policy, characteristics of the sports club), and 4) determinants related to the wider community (i.e., change of social norm with regard to smoking, support from local and national organizations). Conclusion Implementation of an outdoor SFP at sports clubs is feasible because there is a high level of support and experiences are mainly positive. Nevertheless, some situations present challenges to compliance and enforcement. We identified a number of determinants that may facilitate implementation of an outdoor SFP at sports clubs
Genuine Counterfactual Communication with a Nanophotonic Processor
In standard communication information is carried by particles or waves.
Counterintuitively, in counterfactual communication particles and information
can travel in opposite directions. The quantum Zeno effect allows Bob to
transmit a message to Alice by encoding information in particles he never
interacts with. The first suggested protocol not only required thousands of
ideal optical components, but also resulted in a so-called "weak trace" of the
particles having travelled from Bob to Alice, calling the scalability and
counterfactuality of previous proposals and experiments into question. Here we
overcome these challenges, implementing a new protocol in a programmable
nanophotonic processor, based on reconfigurable silicon-on-insulator waveguides
that operate at telecom wavelengths. This, together with our telecom
single-photon source and highly-efficient superconducting nanowire
single-photon detectors, provides a versatile and stable platform for a
high-fidelity implementation of genuinely trace-free counterfactual
communication, allowing us to actively tune the number of steps in the Zeno
measurement, and achieve a bit error probability below 1%, with neither
post-selection nor a weak trace. Our demonstration shows how our programmable
nanophotonic processor could be applied to more complex counterfactual tasks
and quantum information protocols.Comment: 6 pages, 4 figure
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