3,457 research outputs found
Selective and sensitive electrochemical DNA biosensor for the detection of Bacillus anthracis
The development of a selective and sensitive electrochemical DNA biosensor for detection of the
pathogen Bacillus anthracis is proposed here. The technique is based on the characteristic cyclic
voltammetry (CV) redox peaks and the very selective nature of DNA hybridization. The designed
system consists of a self-assembled layer of mercaptohexanol (MCH) and thiol linked probe (ssDNAthiol)
immobilized on gold-modified screen-printed electrodes. This direct detection technique studies
the change in potential and intensity of the surface-modified screen-printed electrodes when a 5mM
Fe(CN)6
3-
solution in 0.1M KClis presented to the electrodic system in the range between -0.5 to 0.7V.
The increase or decrease in the electron transfer along with the varied redox potential during
immobilization of the probe and hybridization of the target was observed as CV peak current and
potential change. The proposed system showed reliable results with sensitivity up to 10pM and
selective enough to distinguish signals from DNA fragments presenting 1bp mismatches. The
fabricated system with the thiol probe once produced could be shelved for 2-3 months.Thus the strong
selective binding nature of the DNA along with the sensitive CV characters, prove to be an efficient
system for reliable detection of pathogens
The Periodic Standing-Wave Approximation: Overview and Three Dimensional Scalar Models
The periodic standing-wave method for binary inspiral computes the exact
numerical solution for periodic binary motion with standing gravitational
waves, and uses it as an approximation to slow binary inspiral with outgoing
waves. Important features of this method presented here are: (i) the
mathematical nature of the ``mixed'' partial differential equations to be
solved, (ii) the meaning of standing waves in the method, (iii) computational
difficulties, and (iv) the ``effective linearity'' that ultimately justifies
the approximation. The method is applied to three dimensional nonlinear scalar
model problems, and the numerical results are used to demonstrate extraction of
the outgoing solution from the standing-wave solution, and the role of
effective linearity.Comment: 13 pages RevTeX, 5 figures. New version. A revised form of the
nonlinearity produces better result
Star formation efficiency in galaxy clusters
The luminous material in clusters of galaxies falls primarily into two forms:
the visible galaxies and the X-ray emitting intra-cluster medium. The hot
intra-cluster gas is the major observed baryonic component of clusters, about
six times more massive than the stellar component. The mass contained within
visible galaxies amounts to approximately 3% of the dynamical mass. Our aim was
to analyze both baryonic components, combining X-ray and optical data of a
sample of five galaxy clusters (Abell 496, 1689, 2050, 2631 and 2667), within
the redshift range 0.03 < z < 0.3. We determined the contribution of stars in
galaxies and the intra-cluster medium to the total baryon budget. We used
public XMM-Newton data to determine the gas mass and to obtain the X-ray
substructures. Using the optical counterparts from SDSS or CFHT we determined
the stellar contribution. We examine the relative contribution of galaxies,
intra-cluster light and intra-cluster medium to baryon budget in clusters
through the stellar-to-gas mass ratio, estimated with use of recent data. We
find that the stellar-to-gas mass ratio within r_500 (the radius which the mean
cluster density exceeds the critical density by a factor of 500), is
anti-correlated with the ICM temperature, ranging from 24% to 6% whereas the
temperature ranges from 4.0 to 8.3 keV. This indicates that less massive cold
clusters are more prolific star forming environments than massive hot clusters.Comment: A&A in press, 15 pages, 9 figure
Epitaxial CuInSe2 thin films grown by molecular beam epitaxy and migration enhanced epitaxy
While CuInSe2 chalcopyrite materials are mainly used in their polycrystalline form to prepare thin film solar cells, epitaxial layers have been used for the characterization of defects. Typically, epitaxial layers are grown by metal-organic vapor phase epitaxy or molecular beam epitaxy (MBE). Here we present epitaxial layers grown by migration enhanced epitaxy (MEE) and compare the materials quality to MBE grown layers. CuInSe2 layers were grown on GaAs (001) substrates by co-evaporation of Cu, In, and Se using substrate temperatures of 450 ÂșC, 530 ÂșC, and 620 ÂșC. The layers were characterized by high resolution X-ray diffraction (HR-XRD), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and atomic force microscopy (AFM). HR-XRD and HR-TEM show a better crystalline quality of the MEE grown layers, and Raman scattering measurements confirm single phase CuInSe2. AFM shows the previously observed faceting of the (001) surface into {112} facets with trenches formed along the [110] direction. The surface of MEE-grown samples appears smoother compared to MBE-grown samples, a similar trend is observed with increasing growth temperature.The authors would like to acknowledge the CAPES (CAPES-INL 04/14), CNPq, and FAPEMIG funding agencies for financial support. We acknowledge the collaboration project with IMMCSIC (AIC-B-2011-0806). P.M.P.S. acknowledges financial support from EU through the FP7 Marie Curie IEF 2012 Action No. 327367.info:eu-repo/semantics/publishedVersio
First joint observations of space weather events over Mexico
Abstract. The Mexican Space Weather Service (SCiESMEX in Spanish) and National Space Weather Laboratory (LANCE in Spanish) were organized in 2014 and in 2016, respectively, to provide space weather monitoring and alerts, as well as scientiïŹc research in Mexico. In this work, we presenttheresultsoftheïŹrstjointobservationsoftwoevents (22 June and 29 September 2015) with our local network of instruments and their related products. This network includes the MEXART radio telescope (solar ïŹare and radio burst), the Compact Astronomical Low-frequency, Low-cost Instrument for Spectroscopy in Transportable Observatories (CALLISTO)attheMEXARTstation(solarradioburst),the Mexico City Cosmic Ray Observatory (cosmic ray ïŹuxes), GPS receiver networks (ionospheric disturbances), and the Teoloyucan Geomagnetic Observatory (geomagnetic ïŹeld). The observations show that we detected signiïŹcant space weather effects over the Mexican territory: geomagnetic and ionospheric disturbances (22 June 2015), variations in cosmicrayïŹuxes,andalsoradiocommunicationsâinterferences (29September2015).Theeffectsoftheseperturbationswere registered,fortheïŹrsttime,usingspaceweatherproductsby SCiESMEX:totalelectroncontent(TEC)maps,regionalgeomagneticindexKmex,radiospectrographsoflowfrequency, and cosmic ray ïŹuxes. These results prove the importance of
monitoring space weather phenomena in the region and the need to strengthening the instrumentation network
Three little pieces for computer and relativity
Numerical relativity has made big strides over the last decade. A number of
problems that have plagued the field for years have now been mostly solved.
This progress has transformed numerical relativity into a powerful tool to
explore fundamental problems in physics and astrophysics, and I present here
three representative examples. These "three little pieces" reflect a personal
choice and describe work that I am particularly familiar with. However, many
more examples could be made.Comment: 42 pages, 11 figures. Plenary talk at "Relativity and Gravitation:
100 Years after Einstein in Prague", June 25 - 29, 2012, Prague, Czech
Republic. To appear in the Proceedings (Edition Open Access). Collects
results appeared in journal articles [72,73, 122-124
Solventes eutéticos naturais profundos (NADES) no preparo de amostras de rocha fosfåtica e suplemento mineral para determinação elementar por técnicas de plasma.
NATURAL DEEP EUTECTIC SOLVENTS (NADES) IN SAMPLE PREPARATION OF PHOSPHATE ROCK AND MINERAL SUPPLEMENT FOR ELEMENTARY DETERMINATION BY PLASMA-BASED TECHNIQUES. Natural deep eutectic solvents (NADES) based on xylitol, citric acid, and malic acid were synthesized and used in ultrasound-assisted extraction (UAE) and heating-bath extraction of phosphate rock and mineral supplement samples. Arsenic, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, P and Zn were determined by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP OES). The results showed the NADES as promising solvents for extraction of inorganic matrices compared to reference values and concentrations obtained using microwave-assisted acid digestion (MW-AD). Significant differences were observed for some elements, suggesting different chemical interactions between the synthesized NADES and each monitored element. For analytes extraction of phosphate rock, UAE presented the best results for As, Cr and P. Zinc was extracted with UAE and heating bath. Concerning mineral supplement, no significant differences were observed for Ca (UAE), Cd (UAE and heating bath), K (UAE and heating bath), Mn (UAE and heating bath), Na (UAE and heating bath), and P (UAE and heating bath). The NADES is a greener and a potentially alternative for the sample preparation compared to the official methods of analysis, can being used as selective extractor solvent in conventional sample preparation methods
Contribution of microscopy for understanding the mechanism of action against trypanosomatids
Transmission electron microscopy (TEM) has proved to be a useful tool to study the ultrastructural alterations and the target organelles of new antitrypanosomatid drugs. Thus, it has been observed that sesquiterpene lactones induce diverse ultrastructural alterations in both T. cruzi and Leishmania spp., such as cytoplasmic vacuolization, appearance of multilamellar structures, condensation of nuclear DNA, and, in some cases, an important accumulation of lipid vacuoles. This accumulation could be related to apoptotic events. Some of the sesquiterpene lactones (e.g., psilostachyin) have also been demonstrated to cause an intense mitochondrial swelling accompanied by a visible kinetoplast deformation as well as the appearance of multivesicular bodies. This mitochondrial swelling could be related to the generation of oxidative stress and associated to alterations in the ergosterol metabolism. The appearance of multilamellar structures and multiple kinetoplasts and flagella induced by the sesquiterpene lactone psilostachyin C indicates that this compound would act at the parasite cell cycle level, in an intermediate stage between kinetoplast segregation and nuclear division. In turn, the diterpene lactone icetexane has proved to induce the external membrane budding on T. cruzi together with an apparent disorganization of the pericellar cytoskeleton. Thus, ultrastructural TEM studies allow elucidating the possible mechanisms and the subsequent identification of molecular targets for the action of natural compounds on trypanosomatids.Fil: Lozano, Esteban SebastiĂĄn. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto de Medicina y BiologĂa Experimental de Cuyo; ArgentinaFil: Spina Zapata, Renata MarĂa. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto de HistologĂa y EmbriologĂa de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias MĂ©dicas. Instituto de HistologĂa y EmbriologĂa de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Barrera, Patricia Andrea. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto de HistologĂa y EmbriologĂa de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias MĂ©dicas. Instituto de HistologĂa y EmbriologĂa de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Tonn, Carlos Eugenio. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Luis. Instituto de Investigaciones en TecnologĂa QuĂmica. Universidad Nacional de San Luis. Facultad de QuĂmica, BioquĂmica y Farmacia. Instituto de Investigaciones en TecnologĂa QuĂmica; ArgentinaFil: Sosa Escudero, Miguel Angel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto de HistologĂa y EmbriologĂa de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias MĂ©dicas. Instituto de HistologĂa y EmbriologĂa de Mendoza Dr. Mario H. Burgos; Argentin
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