Instituto Politécnico Nacional

About: Instituto Politécnico Nacional is a education organization based out in Mexico City, Mexico. It is known for research contribution in the topics: Population & Context (language use). The organization has 43351 authors who have published 63315 publications receiving 938532 citations. The organization is also known as: Instituto Politécnico Nacional & Instituto Politecnico Nacional.

Search for spatially extended fermi large area telescope sources using two years of data

Abstract: Spatial extension is an important characteristic for correctly associating γ-ray-emitting sources with their counterparts at other wavelengths and for obtaining an unbiased model of their spectra. We present a new method for quantifying the spatial extension of sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi). We perform a series of Monte Carlo simulations to validate this tool and calculate the LAT threshold for detecting the spatial extension of sources. We then test all sources in the second Fermi-LAT catalog for extension. We report the detection of seven new spatially extended sources.

Plasmodium falciparum heterochromatin protein 1 binds to tri-methylated histone 3 lysine 9 and is linked to mutually exclusive expression of var genes

Abstract: Increasing experimental evidence shows a prominent role of histone modifications in the coordinated control of gene expression in the human malaria parasite Plasmodium falciparum. The search for the histone-mark-reading machinery that translates histone modifications into biological processes, such as formation of heterochromatin and antigenic variation is of foremost importance. In this work, we identified the first member of a histone modification specific recognition protein, an orthologue of heterochromatin protein 1 (PfHP1). Analysis of the PfHP1 amino-acid sequence revealed the presence of the two characteristic HP1 domains: a chromodomain (CD) and a chromo shadow domain (CSD). Recombinant CD binds to di- and tri-methylated lysine 9 from histone H3, but not to unmodified or methylated histone H3 in lysine 4. PfHP1 is able to interact with itself to form dimers, underlying its potential role in aggregating nucleosomes to form heterochromatin. Antibodies raised against PfHP1 detect this molecule in foci at the perinuclear region. ChIP analysis using anti-PfHP1 shows that this protein is linked to heterochromatin of subtelomeric non-coding repeat regions and monoallelic expression of the major virulence var gene family. This is the first report implicating an HP1 protein in the control of antigenic variation of a protozoan parasite.

Calcium Channels and Ca2+ Fluctuations in Sperm Physiology

Abstract: Generating new life in animals by sexual reproduction depends on adequate communication between mature and competent male and female gametes. Ion channels are instrumental in the dialogue between sperm, its environment, and the egg. The ability of sperm to swim to the egg and fertilize it is modulated by ion permeability changes induced by environmental cues and components of the egg outer layer. Ca(2+) is probably the key messenger in this information exchange. It is therefore not surprising that different Ca(2+)-permeable channels are distinctly localized in these tiny specialized cells. New approaches to measure sperm currents, intracellular Ca(2+), membrane potential, and intracellular pH with fluorescent probes, patch-clamp recordings, sequence information, and heterologous expression are revealing how sperm channels participate in fertilization. Certain sperm ion channels are turning out to be unique, making them attractive targets for contraception and for the discovery of novel signaling complexes.

Combined fit of spectrum and composition data as measured by the Pierre Auger Observatory

Abstract: We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed for energies above $5 \cdot 10^{18}$ eV, i.e.~the region of the all-particle spectrum above the so-called "ankle" feature. The astrophysical model we adopted consists of identical sources uniformly distributed in a comoving volume, where nuclei are accelerated through a rigidity-dependent mechanism. The fit results suggest sources characterized by relatively low maximum injection energies, hard spectra and heavy chemical composition. We also show that uncertainties about physical quantities relevant to UHECR propagation and shower development have a non-negligible impact on the fit results.

Physicochemical characterization of chitosan nanoparticles and nanocapsules incorporated with lime essential oil and their antibacterial activity against food-borne pathogens

Abstract: Lime oil has recognized fungicidal and antibacterial properties. Nanoparticles and nanocapsules are structures that have been developed to overcome the high volatility of essential oils. Chitosan nanoparticles and chitosan nanocapsules incorporated with lime essential oil were synthesized by nanoprecipitation and nanoencapsulation methods, respectively. The samples were characterized by transmission electron microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR), and Z potential was measured. Also, particle size distribution was analyzed by dynamic light scattering (DLS) and the antibacterial activity was studied. According to TEM, the average size of nanocapsules was higher than for nanoparticles. When lime essential oil was incorporated, the particle size increased. Lime essential oil incorporation was evidenced by FTIR. Chitosan nanocapsules showed higher Z potential value compared to chitosan nanoparticles. The antibacterial activity was tested against four food-borne pathogens, being higher for nanoparticles than for nanocapsules. The highest antibacterial activity was observed for chitosan nanoparticles incorporated with lime essential oil applied against Shigella dysenteriae, attaining an inhibition halo (IH) value of 3.5 cm for 40 μL of minimum inhibitory volume (MIV). The novelty of incorporating lime essential oil into chitosan nanoparticles and nanocapsules and the study of their enhancing effect on antibacterial activity are shown in this paper.