1,444,865 research outputs found
Characterization of quantum computable decision problems by state discrimination
One advantage of quantum algorithms over classical computation is the
possibility to spread out, process, analyse and extract information in
multipartite configurations in coherent superpositions of classical states.
This will be discussed in terms of quantum state identification problems based
on a proper partitioning of mutually orthogonal sets of states. The question
arises whether or not it is possible to encode equibalanced decision problems
into quantum systems, so that a single invocation of a filter used for state
discrimination suffices to obtain the result.Comment: 9 page
The combined role of distance and frequency travel restrictions on spread of disease
Travel restrictions have often been used as a measure to combat the spread of
disease -- in particular, they have been extensively applied in 2020 against
coronavirus disease 2019 (COVID-19). How to best restrict travel, however, is
unclear. Most studies and policies simply constrain the distance r individuals
may travel from their home or neighbourhood. However, the epidemic risk is
related not only to distance travelled, but also to frequency of contacts,
which is proxied by the frequency f with which individuals revisit locations
over a given reference period. Inspired by recent literature that uncovers a
clear universality pattern on how r and f interact in routine human mobility,
this paper addresses the following question: does this universal relation
between r and f carry over to epidemic spreading, so that the risk associated
with human movement can be modeled by a single, unifying variable r * f? To
answer this question, we use two large-scale datasets of individual human
mobility to simulate disease spread. Results show that a universal relation
between r and f indeed exists in the context of epidemic spread: in both of the
datasets, the final size and the spatial distribution of the infected
population depends on the product r * f more directly than on the individual
values of r and f. The important implication here is that restricting r (where
you can go), but not f (how frequently), could be unproductive: high frequency
trips to nearby locations can be as dangerous for disease spread as low
frequency trips to distant locations. This counter-intuitive discovery could
explain the modest effectiveness of distance-based travel restrictions and
could inform future policies on COVID-19 and other epidemics.Comment: 8 pages, 7 figure
The Effect of Stellar Rotation on Colour-Magnitude Diagrams: On the apparent presence of multiple populations in intermediate age stellar clusters
A significant number of intermediate age clusters (1-2 Gyr) in the Magellanic
Clouds appear to have multiple stellar populations within them, derived from
bi-modal or extended main sequence turn offs. If this is interpreted as an age
spread, the multiple populations are separated by a few hundred Myr, which
would call into question the long held notion that clusters are simple stellar
populations. Here we show that stellar rotation in stars with masses between
1.2-1.7 Msun can mimic the effect of a double or multiple population, whereas
in actuality only a single population exists. The two main causes of the spread
near the turn-off are the effects of stellar rotation on the structure of the
star and the inclination angle of the star relative to the observer. Both
effects change the observed effective temperature, hence colour, and flux of
the star. In order to match observations, the required rotation rates are
20-50% of the critical rotation, which are consistent with observed rotation
rates of similar mass stars in the Galaxy. We provide scaling relations which
can be applied to non-rotating isochrones in order to mimic the effects of
rotation. Finally, we note that rotation is unlikely to be the cause of the
multiple stellar populations observed in old globular clusters, as low mass
stars (<1 Msun) are not expected to be rapid rotators.Comment: 5 pages, 1 figure, MNRAS letters, in pres
Bail-in credibility: evidence from emerging markets
Purpose Some controversial cases of bail-in in the emerging countries have raised the question about whether for those countries to have in place a regulation for the bail-in is appropriate or not. To assess appropriateness, this paper investigates bail-in credibility among investors, as crucial condition for the credibility's smooth implementation, by measuring the yield spread between bailinable and non-bailinable bonds. Design/methodology/approach The authors compare the yield spread of banks located in emerging countries that have in place a framework for the bail-in to the comparable yield spread measured for banks located in emerging countries without such framework. The comparison permits to detect whether there is a significant difference between the two spreads, which would suggest that bail-in regulation has been deemed credible by market participants where enforced, or not, which in this case would signal a problem of credibility. Findings The authors' results point out a significantly higher yield spread for banks located in emerging countries that have adopted a framework for the bail-in of creditors. Bail-in regulation has, therefore, being deemed credible in the adopting emerging countries, thus ensuring a crucial condition for bail-in regulation's smooth application. The authors also point out bank size and country's gross domestic product (GDP) growth as crucial moderators of bail-in expectations of market participants that can guide the implementation of bail-in rules in emerging countries. Originality/value This paper contributes to the literature on the credibility of bail-in with a new perspective from the emerging countries
Mechanisms of Metastasis in Colorectal Cancer and Metastatic Organotropism: Hematogenous versus Peritoneal Spread
Metastasis is the major cause of death in patients with colorectal carcinoma (CRC). The most common sites of metastasis are the liver and the peritoneum. Peritoneal carcinomatosis is often considered the end stage of the disease after the tumor has spread to the liver. However, almost half of CRC patients with peritoneal carcinomatosis do not present with liver metastasis. This brings up the question of whether peritoneal spread can still be considered as the end stage of a metastasized CRC or whether it should just be interpreted as a site of metastasis alternative to the liver. This review tries to discuss this question and summarize the current status of literature on potential characteristics in tumor biology in the primary tumor, i.e., factors (transcription factors and direct and indirect E-cadherin repressors) and pathways (WNT, TGF-beta, and RAS) modulating EMT, regulation of EMT on a posttranscriptional and posttranslational level (miRNAs), and angiogenesis. In addition to tumor-specific characteristics, factors in the tumor microenvironment, immunological markers, ways of transport of tumor cells, and adhesion molecules appear to differ between hematogenous and peritoneal spread. Factors such as integrins and exosomal integrins, cancer stem cell phenotype, and miRNA expression appear to contribute in determining the metastatic route. We went through each step of the metastasis process comparing hematogenous to peritoneal spread. We identified differences with respect to organotropism, epithelial-mesenchymal transition, angiogenesis and inflammation, and tumor microenvironment which will be further elucidated in this review. A better understanding of the underlying mechanisms and contributing factors of metastasis development in CRC has huge relevance as it is the foundation to help find specific targets for treatment of CRC
Magnetic guidance of charged particles
Many experiments and devices in physics use static magnetic fields to guide
charged particles from a source onto a detector, and we ask the innocent
question: What is the distribution of particle intensity over the detector
surface? One should think that the solution to this seemingly simple problem is
well known. We show that, even for uniform guide fields, this is not the case
and present analytical point spread functions (PSF) for magnetic transport that
deviate strongly from previous results. The "magnetic" PSF shows unexpected
singularities, which were recently also observed experimentally, and which make
detector response very sensitive to minute changes of position, field
amplitude, or particle energy. In the field of low-energy particle physics,
these singularities may become a source of error in modern high precision
experiments, or may be used for instrument tests, for instance in neutrino mass
retardation spectrometers.Comment: 16 pages, 5 figures, version 2: improved approximation metho
Fraud Law and Misinfodemics
During the COVID-19 pandemic, many on whom the public depended for truthful information purposefully or recklessly spread misinformation that put thousands at risk. The term âmisinfodemic,â coined in 2019, describes such events where misinformation facilitates the spread of a disease or causes some other health-related outcome. Though the term was only recently defined, the recent misinfodemic was not a new or novel phenomenon. False information is spread to the public all the time. This often results in harm to public health. False claims are communicated by corporations seeking to mislead the public to make more money, by politicians to gain votes and support, and by media outlets to increase viewership and advertising revenue. Although these and other deceptions of the public for profit might be unethical, they are legal. This Article explores the question of why. There are two key components to this analysis, one centered on tort law and the other on the First Amendment. This Article will focus only on tort law aspects. This Article discusses how fraud law developed to focus almost exclusively on personal deceptions while almost entirely ignoring impersonal deceptions like deceptions of the public. As a result, there is most often no tort remedy available to individuals harmed by misinfodemics. This Article prescribes a fix for this gap in the law: treat fraud on the public like any other fraud by prohibiting misinformation and punishing those who spread it. Precedent and policy support imposing civil remedies against those who purposefully or recklessly mislead the public for gain. The important First Amendment aspects of this issue will be addressed in future scholarship
A heuristic optimization method for mitigating the impact of a virus attack
Taking precautions before or during the start of a virus outbreak can heavily
reduce the number of infected. The question which individuals should be
immunized in order to mitigate the impact of the virus on the rest of
population has received quite some attention in the literature. The dynamics of
the of a virus spread through a population is often represented as information
spread over a complex network. The strategies commonly proposed to determine
which nodes are to be selected for immunization often involve only one
centrality measure at a time, while often the topology of the network seems to
suggest that a single metric is insufficient to capture the influence of a node
entirely.
In this work we present a generic method based on a genetic algorithm (GA)
which does not rely explicitly on any centrality measures during its search but
only exploits this type of information to narrow the search space. The fitness
of an individual is defined as the estimated expected number of infections of a
virus following SIR dynamics. The proposed method is evaluated on two contact
networks: the Goodreau's Faux Mesa high school and the US air transportation
network. The GA method manages to outperform the most common strategies based
on a single metric for the air transportation network and its performance is
comparable with the best performing strategy for the high school network.Comment: To appear in the proceedings of the International Conference on
Computational Science (ICCS) in Barcelona. 11 pages, 5 figure
A method of determining where to target surveillance efforts in heterogeneous epidemiological systems
The spread of pathogens into new environments poses a considerable threat to human, animal, and plant health, and by extension, human and animal wellbeing, ecosystem function, and agricultural productivity, worldwide. Early detection through effective surveillance is a key strategy to reduce the risk of their establishment. Whilst it is well established that statistical and economic considerations are of vital importance when planning surveillance efforts, it is also important to consider epidemiological characteristics of the pathogen in questionâincluding heterogeneities within the epidemiological system itself. One of the most pronounced realisations of this heterogeneity is seen in the case of vector-borne pathogens, which spread between âhostsâ and âvectorsââwith each group possessing distinct epidemiological characteristics. As a result, an important question when planning surveillance for emerging vector-borne pathogens is where to place sampling resources in order to detect the pathogen as early as possible. We answer this question by developing a statistical function which describes the probability distributions of the prevalences of infection at first detection in both hosts and vectors. We also show how this method can be adapted in order to maximise the probability of early detection of an emerging pathogen within imposed sample size and/or cost constraints, and demonstrate its application using two simple models of vector-borne citrus pathogens. Under the assumption of a linear cost function, we find that sampling costs are generally minimised when either hosts or vectors, but not both, are sampled
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