Neutron halos in heavy nuclei -- relativistic mean field approach

Assuming a~simple spherical relativistic mean field model of the nucleus, we estimate the width of the antiproton--neutron annihilation ($\Gamma_n$) and the width of antiproton--proton ($\Gamma_p$) annihilation, in an antiprotonic atom system. This allows us to determine the halo factor $f$, which is then discussed in the context of experimental data obtained in measurements recently done on LEAR utility at CERN. Another quantity which characterizes the deviation of the average nuclear densities ratio from the corresponding ratio of the homogeneous densities is introduced too. It was shown that it is also a good indicator of the neutron halo. The results are compared to experimental data as well as to the data of the simple liquid droplet model of the nuclear densities. The single particle structure of the nuclear density tail is discusssed also.Comment: revtex, 12 pages + 6 postscript figure

Leakage Resilience of the Blom’s Key Distribution Scheme

We initiate the study of the leakage-resilience of the information-theoretic key distribution schemes. Such schemes, originally proposed in the 1980s, have recently attracted a lot of interest in the systems community. This is because, due to their extreme efficiency, they can be executed on low-cost devices such as sensors, where the use of the public-key cryptography is infeasible. We argue that the study of leakage resilience of such schemes is particularly well-motivated, since, unlike more expensive devices, the sensors (or other similar devices) are unlikely to be physically resilient to leakage. We concentrate on the classical scheme of Blom (CRYPTO 1982), since it is known to be optimal in a large class of such schemes. We model the leakage as an input-shrinking function. In this settings we show that Blom’s scheme is leakage-resilient in a very strong model, where the adversary can (1) compromise completely some nodes in a “standard” way, and (2) leak information jointly from the remaining nodes. The amount leakage that we can tolerate can be up to (0.5−ϵ) of the total amount of information on the leaking nodes. We also show that this bound is optimal, by providing an attack that breaks the scheme if more leakage is available to the adversary. This attack works even in a weaker model, where the nodes leak information independently. In the proof we make use of the theory of the randomness extractors. In particular we use the fact that inner product over a finite field is a good 2-source extractor. This is possible since the Blom’s scheme is based on the matrix multiplication

Shot-down stable processes

Bogdan K, Jastrzȩbski K, Kaßmann M, Kijaczko M, Popławski P. Shot-down stable processes. arXiv:2301.12290. 2023.The shot-down process is a strong Markov process which is annihilated, or shot down, when jumping over or to the complement of a given open subset of a vector space. Due to specific features of the shot-down time, such processes suggest new type of boundary conditions for nonlocal differential equations. In this work we construct the shot-down process for the fractional Laplacian in Euclidean space. For smooth bounded sets $D$, we study its transition density and characterize Dirichlet form. We show that the corresponding Green function is comparable to that of the fractional Laplacian with Dirichlet conditions on $D$. However, for nonconvex $D$, the transition density of the shot-down stable process is incomparable with the Dirichlet heat kernel of the fractional Laplacian for $D$. Furthermore, Harnack inequality in general fails for harmonic functions of the shot-down process

Does the MTHFR A1298C polymorphism modulate the cardiorespiratory response to training?

The 5,10-methylenetetrahydrofolate reductase gene (MTHFR) A1298C polymorphic variant is a candidate to explain the individual differences in trainability and response to exercise training. Therefore, the aim of the study was to verify whether the A1298C polymorphism influenced the aerobic and anaerobic performance as well as body and mass composition in young Polish women following low-high impact aerobic exercise training. Two hundred and one women aged 21 ± 1 years (range 19-24) were included in the study. All of them completed a 12-week exercise training program and were measured for selected somatic features, aerobic capacity and cardiorespiratory fitness indices as well as peak anaerobic power and anaerobic capacity, before and after the intervention. A mixed 2 Ã\u97 2 ANOVA for 20 dependent variables grouped in three categories was conducted. No significant interaction of the genotype with training for body mass and body composition variables was observed. Although, there were three significant genotype x training interactions for maximal oxygen uptake variables, regardless of body mass i.e.: for VO2max (p < 0.05), HRmax (p < 0.0001) and HRAT/HRmax (p < 0.0001). Significantly greater improvement in VO2max was gained by the CC+AC group compared to the AA genotype group. The present results support the hypothesis that individual differences in trainability are at least in part determined by the genetic component and MTHFR A1298C seems to be one of the many polymorphisms involved

Covasim:An agent-based model of COVID-19 dynamics and interventions

The COVID-19 pandemic has created an urgent need for models that can project epidemic trends, explore intervention scenarios, and estimate resource needs. Here we describe the methodology of Covasim (COVID-19 Agent-based Simulator), an open-source model developed to help address these questions. Covasim includes country-specific demographic information on age structure and population size; realistic transmission networks in different social layers, including households, schools, workplaces, long-term care facilities, and communities; age-specific disease outcomes; and intrahost viral dynamics, including viral-load-based transmissibility. Covasim also supports an extensive set of interventions, including non-pharmaceutical interventions, such as physical distancing and protective equipment; pharmaceutical interventions, including vaccination; and testing interventions, such as symptomatic and asymptomatic testing, isolation, contact tracing, and quarantine. These interventions can incorporate the effects of delays, loss-to-follow-up, micro-targeting, and other factors. Implemented in pure Python, Covasim has been designed with equal emphasis on performance, ease of use, and flexibility: realistic and highly customized scenarios can be run on a standard laptop in under a minute. In collaboration with local health agencies and policymakers, Covasim has already been applied to examine epidemic dynamics and inform policy decisions in more than a dozen countries in Africa, Asia-Pacific, Europe, and North America