Electronic structure calculations and molecular dynamics simulations with linear system-size scaling

We present a method for total energy minimizations and molecular dynamics simulations based either on tight-binding or on Kohn-Sham hamiltonians. The method leads to an algorithm whose computational cost scales linearly with the system size. The key features of our approach are (i) an orbital formulation with single particle wavefunctions constrained to be localized in given regions of space, and (ii) an energy functional which does not require either explicit orthogonalization of the electronic orbitals, or inversion of an overlap matrix. The foundations and accuracy of the approach and the performances of the algorithm are discussed, and illustrated with several numerical examples including Kohn-Sham hamiltonians. In particular we present calculations with tight-binding hamiltonians for diamond, graphite, a carbon linear chain and liquid carbon at low pressure. Even for a complex case such as liquid carbon -- a disordered metallic system with differently coordinated atoms -- the agreement between standard diagonalization schemes and our approach is very good. Our results establish the accuracy and reliability of the method for a wide class of systems and show that tight binding molecular dynamics simulations with a few thousand atoms are feasible on small workstations

Up-to-date Key Retrieval for Information Centric Networking

Information Centric Networking (ICN) leverages in-network caching to provide efficient data distribution and better performance by replicating contents in multiple nodes to bring content nearer the users. Since contents are stored and replicated into node caches, the content validity must be assured end-to-end. Each content object carries a digital signature to provide a proof of its integrity, authenticity, and provenance. However, the use of digital signatures requires a key management infrastructure to manage the key life cycle. To perform a proper signature verification, a node needs to know whether the signing key is valid or it has been revoked. This paper discusses how to retrieve up-to-date signing keys in the ICN scenario. In the usual public key infrastructure, the Certificate Revocation Lists (CRL) or the Online Certificate Status Protocol (OCSP) enable applications to obtain the revocation status of a certificate. However, the push-based distribution of Certificate Revocation Lists and the request/response paradigm of Online Certificate Status Protocol should be fit in the mechanism of named-data. We consider three possible approaches to distribute up-to-date keys in a similar way to the current CRL and OCSP. Then, we suggest a fourth protocol leveraging a set of distributed notaries, which naturally fits the ICN scenario. Finally, we evaluate the number and size of exchanged messages of each solution, and then we compare the methods considering the perceived latency by the end nodes and the throughput on the network links

Análise do trabalho de algumas ONG em Moçambique

Tese de Mestrado em Estudos AfricanosO panorama mundial mudou após a Segunda Guerra. Começaram a aparecer novos actores internacionais, as ONG, organizações não governamentais. Foi durante as décadas 70-80, (Alves 1996), que se assistiu a uma evolução das ONG para "ONG do desenvolvimento" (ONGd). As ONGd adoptaram uma base mais estruturalista que denunciava a pobreza como consequência das relações económicas internacionais. Neste trabalho foi analisado um caso específico: Maputo, Moçambique. Através de trabalho de campo deu-se atenção sobretudo à relação entre as ONGd e o poder moçambicano. Em 1990 assistiu-se a um aumento das ONG em Moçambique, em paralelo com a elaboração da nova Constituição moçambicana, que permitiu um reconhecimento legal das organizações não governamentais através da lei 8/91. Até agora este é a única base legal para as ONG. Esta lei, apesar de constituir um passo importante na abertura às ONG, mostra muitas limitações. Com efeito, as ONG não são reconhecidas como sujeitos jurídicos, sendo catalogadas como sindicato, congregação religiosa ou empresa. Para obter um quadro o mais completo possível foram entrevistadas ONG laicas, nacionais e estrangeiras, e religiosas sobre as forças e fraquezas de uma ONG que trabalhe no território moçambicano.The world changed after WWII. New international players such as the NGOs (nongovernmental organizations) started becoming prominent on a global scale. During the 1970-1980 (Alves 1996) an evolution towards Development NGOs took place. Development NGOs adopted a more structuralist base that denounced poverty as a consequence of international economic relations. A specific case was analysed in the current work: Maputo, Mozambique. Fieldwork allowed the study of the relations between Development NGOs and Mozambican power. In 1990 there was an increase in the number of NGOs in Mozambique, at the same time that the new Mozambican Constitution was being written, which made a legal acknowledgement of non-governmental organizations possible (law 8/91). This has been the only legal base for NGOs so far. Although it represents an important step towards the acceptance of the NGOs, this law shows many limitations. For practical purposes, the NGOs aren't still recognized as juridical persons, being catalogued as a syndicate, a religious congregation or a company. In order to have the most complete picture possible, several lay, national, foreign and religious NGOs were interviewed regarding the strengths and weaknesses of an NGO working in Mozambican territory

Challenges in diagnosing a peripheral nerve sheath tumor of the ulnar nerve in a dog – a case report

In this case report we present the rare case of a distally located peripheral nerve sheath tumor (PNST) of the left ulnar nerve in a two-year-old female Rottweiler dog. We discuss the clinical and diagnostic findings and the challenges of the diagnosis. The dog was successfully treated with a limb sparing partial neurectomy. After surgery, the dog did not show any pain or lameness on long term follow-up

Optimal Content Prefetching in NDN Vehicle-to-Infrastructure Scenario

Data replication and in-network storage are two basic principles of the Information Centric Networking (ICN) framework in which caches spread out in the network can be used to store the most popular contents. This work shows how one of the ICN architectures, the Named Data Networking (NDN), with content pre-fetching can maximize the probability that a user retrieves the desired content in a Vehicle-to-Infrastructure scenario. We give an ILP formulation of the problem of optimally distributing content in the network nodes while accounting for the available storage capacity and the available link capacity. The optimization framework is then leveraged to evaluate the impact on content retrievability of topology- and network-related parameters as the number and mobility models of moving users, the size of the content catalog and the location of the available caches. Moreover, we show how the proposed model can be modified to find the minimum storage occupancy to achieve a given content retrievability level. The results obtained from the optimization model are finally validated against a Name Data Networking architecture through simulations in ndnSIM

Prenatal Mental Representations in Italian First-Time Mothers Before and During the COVID-19 Pandemic: A Study with Interviews on Maternal Representations During Pregnancy

IntroductionPsychosocial risks increase the levels of not-integrated/ambivalent and restricted/disengaged representations during pregnancy, but no study has specifically analysed the impact of the COVID-19 pandemic on maternal representation styles.Objectives(1) to compare maternal representation styles in primiparous women who became pregnant before and during the COVID-19 pandemic and (2) to analyse the content of representation styles during the COVID-19 pandemic.MethodsA total of 37 Italian pregnant women were recruited from 2019 to 2021. The sample was divided into two groups: the pre-COVID-19 group (22 women, mean age = 33.14 years; SD = 3.78) and the COVID-19 group (15 women, mean age = 35.9 years; SD = 4.6). Interviews on maternal representations during pregnancy were administered and analysed for style and content. Results: Women during the COVID-19 pandemic reported more restricted/disengaged and less integrated/balanced representation styles than women pre-COVID-19. Content analysis showed that the COVID-19 pandemic led women to focus more on concrete aspects of pregnancy in lieu of emotional aspects, thus leading them to develop more restricted/disengaged representation styles. Conclusions for practiceIn future pandemics pregnant women should be supported in focusing their attention to emotions, sensations and fantasies about themselves as mothers and their children

Total energy global optimizations using non orthogonal localized orbitals

An energy functional for orbital based $O(N)$ calculations is proposed, which depends on a number of non orthogonal, localized orbitals larger than the number of occupied states in the system, and on a parameter, the electronic chemical potential, determining the number of electrons. We show that the minimization of the functional with respect to overlapping localized orbitals can be performed so as to attain directly the ground state energy, without being trapped at local minima. The present approach overcomes the multiple minima problem present within the original formulation of orbital based $O(N)$ methods; it therefore makes it possible to perform $O(N)$ calculations for an arbitrary system, without including any information about the system bonding properties in the construction of the input wavefunctions. Furthermore, while retaining the same computational cost as the original approach, our formulation allows one to improve the variational estimate of the ground state energy, and the energy conservation during a molecular dynamics run. Several numerical examples for surfaces, bulk systems and clusters are presented and discussed.Comment: 24 pages, RevTex file, 5 figures available upon reques

Neuromarketing empirical approaches and food choice: A systematic review

Consumers' food choices are often driven by reasons of which consumers are not fully aware. Decision-making about food is influenced by a complex set of emotions, feelings, attitudes, and values that are impossible to assess simply by asking consumers their opinions. Indeed, traditional techniques, such as self-reports or interviews, mainly allow the measurement of conscious and rational reactions to a product or advertising. Recently, there has been a rapidly growing interest in the multidisciplinary field of “neuromarketing,” which takes advantage of neuroscientific techniques to study consumer behavior. This discipline applies neuroscientific methods and tools that allow the measurement of consumers' emotional and spontaneous reactions in a more objective and observable way. The aim of this paper is (a) to describe neuromarketing's underlying assumptions, techniques, and the advantages of this perspective, examining the scientific literature on the use of neuromarketing in food studies; and (b) to suggest best practices to apply this novel approach in the food marketing domain, with a specific focus on non-invasive methods. Finally, although the perception of nutritional elements has already been explored, the health content of labels, the presence of additives, and the evaluation of the information conveyed by food packaging remain other possible elements of interest in future food neuromarketing research

Large scale quantum simulations: C_60 impacts on a semiconducting surface

We present tight binding molecular dynamics simulations of C_60 collisions on the reconstructed diamond(111) surface, carried out with an O(N) method and with cells containing 1140 atoms. The results of our simulations are in very good agreement with experiments performed under the same impact conditions. Furthermore our calculations provide a detailed characterization of the microscopic processes occuring during the collision, and allow the identification of three impact regimes, as a function of the fullerene incident energy. Finally, the study of the reactivity between the cluster and the surface gives insight into the deposition mechanisms of C_60 on semiconducting substrates