Cell bystander effect induced by radiofrequency electromagnetic fields and magnetic nanoparticles

Induced effects by direct exposure to ionizing radiation (IR) are a central issue in many fields like radiation protection, clinic diagnosis and oncological therapies. Direct irradiation at certain doses induce cell death, but similar effects can also occur in cells no directly exposed to IR, a mechanism known as bystander effect. Non-IR (radiofrequency waves) can induce the death of cells loaded with MNPs in a focused oncological therapy known as magnetic hyperthermia. Indirect mechanisms are also able to induce the death of unloaded MNPs cells. Using in vitro cell models, we found that colocalization of the MNPs at the lysosomes and the non-increase of the temperature induces bystander effect under non-IR. Our results provide a landscape in which bystander effects are a more general mechanism, up to now only observed and clinically used in the field of radiotherapy.Comment: 16 pages, 4 figures, submitted to International Journal of Radiation Biolog

Computing with cells: membrane systems - some complexity issues.

Membrane computing is a branch of natural computing which abstracts computing models from the structure and the functioning of the living cell. The main ingredients of membrane systems, called P systems, are (i) the membrane structure, which consists of a hierarchical arrangements of membranes which delimit compartments where (ii) multisets of symbols, called objects, evolve according to (iii) sets of rules which are localised and associated with compartments. By using the rules in a nondeterministic/deterministic maximally parallel manner, transitions between the system configurations can be obtained. A sequence of transitions is a computation of how the system is evolving. Various ways of controlling the transfer of objects from one membrane to another and applying the rules, as well as possibilities to dissolve, divide or create membranes have been studied. Membrane systems have a great potential for implementing massively concurrent systems in an efficient way that would allow us to solve currently intractable problems once future biotechnology gives way to a practical bio-realization. In this paper we survey some interesting and fundamental complexity issues such as universality vs. nonuniversality, determinism vs. nondeterminism, membrane and alphabet size hierarchies, characterizations of context-sensitive languages and other language classes and various notions of parallelism

Protein adsorption onto Fe3O4 nanoparticles with opposite surface charge and its impact on cell uptake

Nanoparticles (NPs) engineered for biomedical applications are meant to be in contact with protein-rich physiological fluids. These proteins are usually adsorbed onto the NP surface, forming a swaddling layer called protein corona that influences cell internalization. We present a study on protein adsorption onto different magnetic NPs (MNPs) when immersed in cell culture medium, and how these changes affect the cellular uptake. Two colloids with magnetite cores of 25 nm, same hydrodynamic size and opposite surface charge were in situ coated with (a) positive polyethyleneimine (PEI-MNPs) and (b) negative poly(acrylic acid) (PAA-MNPs). After few minutes of incubation in cell culture medium the wrapping of the MNPs by protein adsorption resulted in a 5-fold size increase. After 24 h of incubation large MNP-protein aggregates with hydrodynamic sizes 1500 to 3000 nm (PAA-MNPs and PEI-MNPs respectively) were observed. Each cluster contained an estimated number of magnetic cores between 450 and 1000, indicating the formation of large aggregates with a "plum pudding" structure of MNPs embedded into a protein network of negative surface charge irrespective of the MNP_core charge. We demonstrated that PEI-MNPs are incorporated in much larger amounts than the PAA-MNPs units. Quantitative analysis showed that SH-SY5Y cells can incorporate 100 per cent of the added PEI-MNPs up to about 100 pg per cell, whereas for PAA-MNPs the uptake was less than 50 percent. The final cellular distribution showed also notable differences regarding partial attachment to the cell membrane. These results highlight the need to characterize the final properties of MNPs after protein adsorption in biological media, and demonstrate the impact of these properties on the internalization mechanisms in neural cells.Comment: 32 pages, 10 figure

Supersymmetric free-damped oscillators: Adaptive observer estimation of the Riccati parameter

A supersymmetric class of free damped oscillators with three parameters has been obtained in 1998 by Rosu and Reyes through the factorization of the Newton equation. The supplementary parameter is the integration constant of the general Riccati solution. The estimation of the latter parameter is performed here by employing the recent adaptive observer scheme of Besancon et al., but applied in a nonstandard form in which a time-varying quantity containing the unknown Riccati parameter is estimated first. Results of computer simulations are presented to illustrate the good feasibility of this approach for a case in which the estimation is not easily accomplished by other meansComment: 8 pages, 6 figure

Small steps towards Grand Unification and the electron/positron excesses in cosmic-ray experiments

We consider a small extension of the standard model by adding two Majorana fermions; those are adjoint representations of the SU(2)_L and SU(3)_c gauge groups of the standard model. In this extension, the gauge coupling unification at an energy scale higher than 10^{15} GeV is realized when the masses of the triplet and the octet fermions are smaller than 10^4 GeV and 10^{12} GeV, respectively. We also show that an appropriate symmetry ensures a long lifetime of the neutral component of the triplet fermion whose thermal relic density naturally explains the observed dark matter density. The electron/positron excesses observed in recent cosmic-ray experiments can be also explained by the decay of the triplet fermion.Comment: 11 pages, 5 figure

Tratamiento de lesiones de caries microcavitadas mediante sellantes de resina y vidrio ionómero en dientes permanentes de niños de 6 a 11 años, seguimiento a 6 meses, 2015.

82 p.Se llevó a cabo un estudio Clínico Controlado Aleatorizado (RCT) donde dos tipos de sellantes fueron aplicados sobre primeros molares permanentes en lesiones ICDAS II código 3. El RCT se llevó a cabo en niños de entre 6 y 11 años que se atienden en las Clínicas Odontológicas de la Universidad de Talca, en Talca. Se trataron 151 lesiones de caries con dos tipos de materiales en base a resinas o vidrio ionómero (VI), las que fueron divididas de forma aleatoria. Los sujetos tuvieron una evaluación tanto clínica como radiográfica, en tiempo “0” (baseline) y un seguimiento a los 6 meses. Se evaluó la progresión de caries y retención del material utilizado, y a su vez se asociaron con respecto a diferentes variables sociodemográficas. Al seguimiento de los 6 meses, los resultados indicaron que no existe progresión de caries tanto clínica como radiográfica al comparar ambos materiales. No hubo asociación entre progresión de caries, el éxito clínico y las diferentes variables sociodemográficas. Además en este estudio, al comparar el sellante de resina y de VI, se demostró que ambos materiales son igualmente efectivos en la detención de caries. En cuanto a la retención, no hubo diferencias entre los dos tipos de sellantes. Dado que el estudio se realizó en un tiempo limitado, se hace necesario continuar con el seguimiento y controles posteriores para obtener conclusiones más definitivas. Palabras claves:Sellante de resina, sellante de vidrio ionómero, lesión de caries, primer molar permanente, ensayo clínico y odontología mínimamente invasiva./ABSTRACT: It was carried out a Randomized Clinical Trial (RCT), where two types of sealant were applied on the first permanent molars in International Caries Detection and Assessment System II (ICDAS) code 3 lesions. The RCT was conducted on children between 6 and 11 years old that are treated on the Dental Clinic of Universidad de Talca, in Talca. To treat the 151 caries lesions it was used two types of materials based on resin or Glass Ionomer Cements (GIC). Those materials were divided randomly. The participants were first evaluated both clinical and radiographic in a baseline, and then, after six months, they were monitored. The progression of caries and the material retention were evaluated and then associated with different sociodermographic variables. The result of the six-month-monitoring showed that there is no caries progression in both clinical and radiographic, when both materials are compared. Moreover, there was no association between the caries progression, the clinic success, and the different sociodemographic variables. Besides, this study demonstrated that when sealant of resin and GIC are compared they are equally effective when detecting caries. Finally, regarding to the material retention, there were no differences between both types of sealant. Since the study was carried out in a limited time, it is necessary to continue with the monitoring and subsequent medical examinations to obtain more definitive conclusions. Key Words: Resin sealant, glass ionomer sealant, caries lesion, first permanent molars, clinical trial and minimally invasive dentistry

On the Commutative Equivalence of Context-Free Languages

The problem of the commutative equivalence of context-free and regular languages is studied. In particular conditions ensuring that a context-free language of exponential growth is commutatively equivalent with a regular language are investigated