373 research outputs found
Social Networks through the Prism of Cognition
Human relations are driven by social events - people interact, exchange
information, share knowledge and emotions, or gather news from mass media.
These events leave traces in human memory. The initial strength of a trace
depends on cognitive factors such as emotions or attention span. Each trace
continuously weakens over time unless another related event activity
strengthens it. Here, we introduce a novel Cognition-driven Social Network
(CogSNet) model that accounts for cognitive aspects of social perception and
explicitly represents human memory dynamics. For validation, we apply our model
to NetSense data on social interactions among university students. The results
show that CogSNet significantly improves quality of modeling of human
interactions in social networks
Recombinant Lactococcus lactis expressing haemagglutinin from a polish avian H5N1 isolate and its immunological effect in preliminary animal trials.
Lactic acid bacteria (LAB) are Gram-positive, non-pathogenic microorganisms that are gaining much interest as antigen producers for development of live vaccine vectors. Heterologous proteins of different origin have been successfully expressed in such LAB species as Lactococcus lactis. Recombinant L. lactis strains have been shown to induce specific local and systemic immune responses against various antigens. Our study aimed at constructing a L. lactis strain expressing haemagglutinin of the Polish avian H5H1 influenza isolate and examining its effect on animals. Expression of the cloned H5 gene was achieved using the nisin-controlled gene expression system. Detection of the intracellular H5 antigen produced in L. lactis was performed by Western blot analysis and confirmed using Mass Spectrometry. The potential of L. lactis recombinant cells to induce an immune response was examined by setting up preliminary immunization trials on mice and chicken. Obtained sera were tested for specific antibodies by ELISA assays. The results of these preliminary studies are a promising step toward developing a vaccine against the avian bird flu using Lactococcus lactis cells as bioreactors for efficient antigen production and delivery to the mucosal surface
Ferns and lycophytes of Celaque National Park, Honduras
A recent survey of the montane cloud forest of Celaque has added 20 new additions to the fern flora of Celaque National Park, Honduras. A list of all the ferns and lycophytes recorded for the park is provided
Origin of the Verwey transition in magnetite: Group theory, electronic structure, and lattice dynamics study
The Verwey phase transition in magnetite has been analyzed using the group
theory methods. It is found that two order parameters with the symmetries
and induce the structural transformation from the high-temperature
cubic to the low-temperature monoclinic phase. The coupling between the order
parameters is described by the Landau free energy functional. The electronic
and crystal structure for the cubic and monoclinic phases were optimized using
the {\it ab initio} density functional method. The electronic structure
calculations were performed within the generalized gradient approximation
including the on-site interactions between 3d electrons at iron ions -- the
Coulomb element and Hund's exchange . Only when these local interactions
are taken into account, the phonon dispersion curves, obtained by the direct
method for the cubic phase, reproduce the experimental data. It is shown that
the interplay of local electron interations and the coupling to the lattice
drives the phonon order parameters and is responsible for the opening of the
gap at the Fermi energy. Thus, it is found that the metal-insulator transition
in magnetite is promoted by local electron interactions, which significantly
amplify the electron-phonon interaction and stabilize weak charge order
coexisting with orbital order of the occupied states at Fe ions. This
provides a scenario to understand the fundamental problem of the origin of the
Verwey transition in magnetite.Comment: 17 pages, 5 figures, 8 tables. Accepted version to be published in
Phys. Rev.
The Memory-Modifying Potential of Optogenetics and the Need for Neuroethics
Optogenetics is an invasive neuromodulation technology involving the use of light to control the activity of individual neurons. Even though optogenetics is a relatively new neuromodulation tool whose various implications have not yet been scrutinized, it has already been approved for its first clinical trials in humans. As optogenetics is being intensively investigated in animal models with the aim of developing novel brain stimulation treatments for various neurological and psychiatric disorders, it appears crucial to consider both the opportunities and dangers such therapies may offer. In this review, we focus on the memory-modifying potential of optogenetics, investigating what it is capable of and how it differs from other memory modification technologies (MMTs). We then outline the safety challenges that need to be addressed before optogenetics can be used in humans. Finally, we re-examine crucial neuroethical concerns expressed in regard to other MMTs in the light of optogenetics and address those that appear to be unique to the memory-modifying potential of optogenetic technology
Post- i transhumanizm w kontekście wybranych zjawisk artystycznych technokultury
Creations of many contemporary artists indicate the emergence of technoculture. Although artistic manifestations of technoculture may appear to be a provocation, they encourage fundamental ontological questions, such as whether a person has unchanging nature; what was and is our relationship to the Other, and what it should be; to what extent can body and mind be altered before they stop being “human”; what is the future of our species. To properly understand the works of technoculture artists, it appears necessary to have a thorough grasp post- and transhumanism as their key sources of inspiration. As a result, the developed tools will be employed to indicate which aspects of technoculture are a manifestation of post- and transhumanist ideas. This analysis is based primarily on the works of Stelarc and Orlan – two widely commented artists of technoculture
Personality and Authenticity in Light of the Memory-Modifying Potential of Optogenetics
There has been a growing interest in research concerning memory modification technologies (MMTs) in recent years. Neuroscientists and psychologists are beginning to explore the prospect of controllable and intentional modification of human memory. One of the technologies with the greatest potential to this end is optogenetics - an invasive neuromodulation technique involving the use of light to control the activity of individual brain cells. It has recently shown the potential to modify specific long-term memories in animal models in ways not yet possible with other MMTs. As the therapeutic potential of optogenetics has already prompted approval of the first human trials, it is especially important and timely to consider the opportunities and dangers this technology may entail. In this article, we focus on possible consequences of optogenetics as an MMT by analyzing fundamental threats potentially associated with memory modifications: the potential disruption of personality and authenticity
Extension of Frohlich's method to 4-fermion interactions
Higher order terms of the transformed electron-phonon Hamiltonian, obtained
by performing the Frohlich's transformation, are investigated. The influence of
terms discarded by Frohlich (in particular those proportional to the third
power of electron-phonon coupling) on the effective Hamiltonian is examined. To
this end a second Frohlich-type transformation is performed, which yields,
among others, an effective 4-electron interaction. This interaction is reduced
to a form admitting solution of thermodynamics. The form of the coupling of the
4-electron interaction is found. By applying standard approximations, it is
shown that this interaction is attractive with interaction coupling given by -
D_{k_F}^6 / \omega_{k_F}^5, where D_{k} is electron-phonon coupling,
\omega_{k}$ is phonon energy and k_F is Fermi momentum.
The form of higher order terms of the original Frohlich-transformed H_{e-ph}
are also found, up to terms proportional to the 6-th power of the coupling,
that is up to those, which yield the effective 4-electron interactions.Comment: REVTeX4, 25 pages; major changes: added section and appendix about
the form of 4-fermion interaction coupling, typos correcte
Structure and elastic properties of Mg(OH) from density functional theory
The structure, lattice dynamics and mechanical properties of the magnesium
hydroxide have been investigated with static density functional theory
calculations as well as \it {ab initio} molecular dynamics. The hypothesis of a
superstructure existing in the lattice formed by the hydrogen atoms has been
tested. The elastic constants of the material have been calculated with static
deformations approach and are in fair agreement with the experimental data. The
hydrogen subsystem structure exhibits signs of disordered behaviour while
maintaining correlations between angular positions of neighbouring atoms. We
establish that the essential angular correlations between hydrogen positions
are maintained to the temperature of at least 150 K and show that they are well
described by a physically motivated probabilistic model. The rotational degree
of freedom appears to be decoupled from the lattice directions above 30K
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