1,076 research outputs found
Zone methods and the fermion sign problem
We review a recently proposed approach to the problem of alternating signs
for fermionic many body Monte Carlo simulations in finite temperature
simulations. We derive an estimate for fermion wandering lengths and introduce
the notion of permutation zones, special regions of the lattice where identical
fermions may interchange and outside of which they may not. Using successively
larger permutation zones, one can extrapolate to obtain thermodynamic
observables in regimes where direct simulation is impossible.Comment: 3 pages, 1 figure, Lattice2002(algor
Computing : An elementary approach in time
We present an efficient and elementary algorithm for computing the number of
primes up to in time, improving upon the existing
combinatorial methods that require time. Our method has
a similar time complexity to the analytical approach to prime counting, while
avoiding complex analysis and the use of arbitrary precision complex numbers.
While the most time-efficient version of our algorithm requires
space, we present a continuous space-time trade-off,
showing, e.g., how to reduce the space complexity to
while slightly increasing the time complexity to . We
apply our techniques to improve the state-of-the-art complexity of elementary
algorithms for computing other number-theoretic functions, such as the the
Mertens function (in time compared to the known
), summing Euler's totient function, counting square-free
numbers and summing primes. Implementation code is provided
A Framework for Single-Item NFT Auction Mechanism Design
Lately, Non-Fungible Tokens (NFTs), i.e., uniquely discernible assets on a
blockchain, have skyrocketed in popularity by addressing a broad audience.
However, the typical NFT auctioning procedures are conducted in various, ad hoc
ways, while mostly ignoring the context that the blockchain provides. One of
the main targets of this work is to shed light on the vastly unexplored design
space of NFT Auction Mechanisms, especially in those characteristics that
fundamentally differ from traditional and more contemporaneous forms of
auctions. We focus on the case that bidders have a valuation for the auctioned
NFT, i.e., what we term the single-item NFT auction case. In this setting, we
formally define an NFT Auction Mechanism, give the properties that we would
ideally like a perfect mechanism to satisfy (broadly known as incentive
compatibility and collusion resistance) and prove that it is impossible to have
such a perfect mechanism. Even though we cannot have an all-powerful protocol
like that, we move on to consider relaxed notions of those properties that we
may desire the protocol to satisfy, as a trade-off between implementability and
economic guarantees. Specifically, we define the notion of an
equilibrium-truthful auction, where neither the seller nor the bidders can
improve their utility by acting non-truthfully, so long as the counter-party
acts truthfully. We also define asymptotically second-price auctions, in which
the seller does not lose asymptotically any revenue in comparison to the
theoretically-optimal (static) second-price sealed-bid auction, in the case
that the bidders' valuations are drawn independently from some distribution. We
showcase why these two are very desirable properties for an auction mechanism
to enjoy, and construct the first known NFT Auction Mechanism which provably
possesses such formal guarantees.Comment: To appear in ACM DeFi 2022. 17 page
The role of mentorship in protege performance
The role of mentorship on protege performance is a matter of importance to
academic, business, and governmental organizations. While the benefits of
mentorship for proteges, mentors and their organizations are apparent, the
extent to which proteges mimic their mentors' career choices and acquire their
mentorship skills is unclear. Here, we investigate one aspect of mentor
emulation by studying mentorship fecundity---the number of proteges a mentor
trains---with data from the Mathematics Genealogy Project, which tracks the
mentorship record of thousands of mathematicians over several centuries. We
demonstrate that fecundity among academic mathematicians is correlated with
other measures of academic success. We also find that the average fecundity of
mentors remains stable over 60 years of recorded mentorship. We further uncover
three significant correlations in mentorship fecundity. First, mentors with
small mentorship fecundity train proteges that go on to have a 37% larger than
expected mentorship fecundity. Second, in the first third of their career,
mentors with large fecundity train proteges that go on to have a 29% larger
than expected fecundity. Finally, in the last third of their career, mentors
with large fecundity train proteges that go on to have a 31% smaller than
expected fecundity.Comment: 23 pages double-spaced, 4 figure
Lipopolysaccharide (LPS) Inner-Core Phosphates Are Required for Complete LPS Synthesis and Transport to the Outer Membrane in Pseudomonas aeruginosa PAO1
Gram-negative outer membrane (OM) integrity is maintained in part by Mg2+ cross-links between phosphates on lipid A and on core sugars of adjacent lipopolysaccharide (LPS) molecules. In contrast to other Gram-negative bacteria, waaP, encoding an inner-core kinase, could not be inactivated in Pseudomonas aeruginosa. To examine this further, expression of the kinases WaaP or WapP/WapQ/PA5006 was placed under the control of the arabinose-regulated pBAD promoter. Growth of these strains was arabinose dependent, confirming that core phosphorylation is essential in P. aeruginosa. Transmission electron micrographs of kinase-depleted cells revealed marked invaginations of the inner membrane. SDS-PAGE of total LPS from WaaP-depleted cells showed accumulation of a fast-migrating band. Mass spectrometry (MS) analysis revealed that LPS from these cells exhibits a unique truncated core consisting of two 3-deoxy-d-manno-octulosonic acids (Kdo), two l-glycero-d-manno-heptoses (Hep), and one hexose but completely devoid of phosphates, indicating that phosphorylation by WaaP is necessary for subsequent core phosphorylations. MS analysis of lipid A from WaaP-depleted cells revealed extensive 4-amino-4-deoxy-l-arabinose modification. OM prepared from these cells by Sarkosyl extraction of total membranes or by sucrose density gradient centrifugation lacked truncated LPS. Instead, truncated LPS was detected in the inner membrane fractions, consistent with impaired transport/assembly of this species into the OM
Assessing Vividness of Mental Imagery: The Plymouth Sensory Imagery Questionnaire
Publisher allows archiving of submitted msMental imagery may occur in any sensory modality, although visual imagery has been most studied. A sensitive measure of the vividness of imagery across a range of modalities is needed: the shorter version of Bett’s QMI (Sheehan, 1967) uses outdated items and has an unreliable factor structure. We report the development and initial validation of the Plymouth Sensory Imagery Questionnaire (Psi-Q) comprising items for each of the following modalities: Vision, Sound, Smell, Taste, Touch, Bodily Sensation and Emotional Feeling. An Exploratory Factor Analysis on a 35-item form indicated that these modalities formed separate factors, rather than a single imagery factor, and this was replicated by confirmatory factor analysis. The Psi-Q was validated against the Spontaneous Use of Imagery Scale (Reisberg, Pearson & Kosslyn, 2003) and Marks’ (1995) Vividness of Visual Imagery Questionnaire-2. A short 21-item form comprising the best three items from the seven factors correlated with the total score and subscales of the full form, and with the VVIQ-2. Inspection of the data shows that while visual and sound imagery is most often rated as vivid, individuals who rate one modality as strong and the other as weak are not uncommon. Findings are interpreted within a working memory framework and point to the need for further research to identify the specific cognitive processes underlying the vividness of imagery across sensory modalities
Defining minimum income (and living) standards in Europe : methodological issues and policy debates
Minimum income protection is gaining new significance in European social policy. In an effort to promote social inclusion, the European Parliament has called on the European Commission and EU Member States to guarantee the minimum right to social safety nets. The Commission has been considering, in the context of the Europe 2020 strategy, the possibility of setting minimum standards for social protection. It is timely then to survey the debates surrounding minimum income standards for Europe and some of the different technologies available for setting reference budgets. A European needs-based (minimum) social protection floor should help guard against poverty and exclusion, but there can be no ‘one size fits all’ in Europe. For it is equally clear that higher social standards of protection may be required by citizens in more affluent parts of Europe. How can such distinctions be made, and what are the challenges arising from doing so
General scientific guidance for stakeholders on health claim applications
The European Food Safety Authority (EFSA) asked the Panel on Dietetic Products Nutrition and Allergies (NDA) to update the General guidance for stakeholders on the evaluation of Article 13.1, 13.5 and 14 health claims published in March 2011. Since then, the NDA Panel has completed the evaluation of Article 13.1 claims except for claims put on hold by the European Commission, and has evaluated additional health claim applications submitted pursuant to Articles 13.5, 14 and also 19. In addition, comments received from stakeholders indicate that general issues that are common to all health claims need to be further clarified and addressed. This guidance document aims to explain the general scientific principles applied by the NDA Panel for the evaluation of all health claims and outlines a series of steps for the compilation of applications. The general guidance document represents the views of the NDA Panel based on the experience gained to date with the evaluation of health claims, and it may be further updated, as appropriate, when additional issues are addressed
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