832 research outputs found

    Gelation of n3p3[nh(ch2)3si(oet)3]6-n [x]n x = nh(ch2)3si(oet)3, nch3(ch2)3cn and oc6h4(ch2)cn, n = 0 or 3 at the liquid/air/interface

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    Indexación: ScieloThe compounds N3P3[NH(CH2)3Si(OEt)3]6 (1), N3P3[NH(CH2)3Si(OEt)3]3[NCH3(CH2)3CN]3 (2) and N3P3[NH(CH2)3Si(OEt)3]3 [HOC6H4(CH2)CN]3 (3) undergo slow gelation at the interface oil/air at low temperatures to give perfect gels G1, G2 and G3 respective ly. TEM analysis reveals nanoparticles of silica with mean size of about 10 nm. Pyrolysis under air at 800 °C of these gels affords a mixture of mainly Si5(PO4)6O, SiP2O7 and SiO2. Gelation and pyrolysis products were characterized by IR, solid-state NMR, TEM, SEM-EDAX microscopy and X-ray diffraction. The sol-gel process in the interface liquid /air is discussed in comparison with the usual sol-gel solution process.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072010000300031&nrm=is

    Sol-gel incorporation of organometallic compounds into silica: useful precursors to metallic nanostructured materials

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    Indexación: Web of Science; ScieloLa inclusión del MLN organometálica = HOC 6 H 4 CH 2 CN • Mo (CO) 5 (6) en sílice amorfa con los precursores TEOS gelificante y N 3 P 3 {NH [CH 2 ] 3 Si [OEt] 3 } 6 permitirse los geles (MLN) ( SiO 2 ) n . Los nanocompuestos híbridos inorgánicos-orgánicos se piroliza bajo aire a 800 º C para dar óxidos nanoestructurados metálicos y / o pirofosfatos de metal (fosfatos) incluidos en las matrices de sílice. La morfología de los nanocompuestos monolíticas exhiben una fuerte dependencia con el precursor del gel utilizado es principalmente laminar para aquellos preparados utilizando N 3 P 3 {NH [CH 2 ] 3 Si [OEt] 3 } como gelificante. Las imágenes de TEM muestran la forma y tamaño diferentes, tales como nanopartículas circulares, nanocables y aglomerados en algunos casos con tamaños de 20 nm para las nanoestructuras circulares y de diámetro aproximadamente 25 nm para los nanocables.Inclusion of the organometallic MLn = [HOC5H4N•Cp2TiCl][PF6] (1), HOC5H4N-W(CO)5 (2), HOC5H4N•Mo(CO)5 (3), [HOC6H4CH2CN•Cp2TiCl][PF6] (4), HOC6H4CH2CN•W(CO)5 (5) and HOC6H4CH2CN•Mo(CO)5 (6) into amorphous silica using the gelator precursor TEOS and N3P3{NH[CH2]3Si[OEt]3}6 afford the gels (MLn)(SiO2)n. The inorganic-organic hybrid nanocomposites were pyrolyzed under air at 800°C to give nanostructured metal oxides and/or metal pyrophosphates (phosphates) included in the silica matrices. The morphology of the monolithic nanocomposites exhibited a strong dependence on the gel precursor used being mainly laminar for those prepared using N3P3{NH[CH2]3Si[OEt]3} as gelator. TEM images show different shape and size such as circular nanoparticles, nanocables and agglomerates in some cases with sizes of 20 nm for the circular nanostructures, and diameter about 25 nm for the nanocables.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072012000200021&nrm=is

    Els mestres dels nostres mestres

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    Higgs-otic Inflation and Moduli Stabilization

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    We study closed-string moduli stabilization in Higgs-otic inflation in Type IIB orientifold backgrounds with fluxes. In this setup large-field inflation is driven by the vacuum energy of mobile D7-branes. Imaginary selfdual (ISD) three-form fluxes in the background source a ÎĽ\mu-term and the necessary monodromy for large field excursions while imaginary anti-selfdual (IASD) three-form fluxes are sourced by non-perturbative contributions to the superpotential necessary for moduli stabilization. We analyze K\"ahler moduli stabilization and backreaction on the inflaton potential in detail. Confirming results in the recent literature, we find that integrating out heavy K\"ahler moduli leads to a controlled flattening of the inflaton potential. We quantify the flux tuning necessary for stability even during large-field inflation. Moreover, we study the backreaction of supersymmetrically stabilized complex structure moduli and the axio-dilaton in the K\"ahler metric of the inflaton. Contrary to previous findings, this backreaction can be pushed far out in field space if a similar flux tuning as in the K\"ahler sector is possible. This allows for a trans-Planckian field range large enough to support inflation.Comment: 42 pages, 10 figures, v2: comments and references added. Published versio

    The DBI Action, Higher-derivative Supergravity, and Flattening Inflaton Potentials

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    In string theory compactifications it is common to find an effective Lagrangian for the scalar fields with a non-canonical kinetic term. We study the effective action of the scalar position moduli of Type II Dpp-branes. In many instances the kinetic terms are in fact modified by a term proportional to the scalar potential itself. This can be linked to the appearance of higher-dimensional supersymmetric operators correcting the K\"ahler potential. We identify the supersymmetric dimension-eight operators describing the α′\alpha' corrections captured by the D-brane Dirac-Born-Infeld action. Our analysis then allows an embedding of the D-brane moduli effective action into an N=1\mathcal N = 1 supergravity formulation. The effects of the potential-dependent kinetic terms may be very important if one of the scalars is the inflaton, since they lead to a flattening of the scalar potential. We analyze this flattening effect in detail and compute its impact on the CMB observables for single-field inflation with monomial potentials.Comment: 25 pages, 3 figures. Comments and references added. Published versio

    Effects of Multicomponent Physical Exercise Programs on Physical Fitness in People with Intellectual Disabilities: A Systematic Review

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    People with intellectual disabilities (ID) have high rates of overweight and obesity, heart and metabolic diseases, and low motor development. These factors compromise functional independence and autonomy in activities of daily living. The objective of this study was to clarify the design and implementation of multicomponent physical exercise programs (MPEPs) and evaluate their effects on physical fitness in people with ID. A search for scientific articles in English published before 2022 was conducted usingWeb of Science, PubMed, Scopus, and Science Direct databases. Scientific papers describing the effects of MPEPs on physical fitness in people with ID were considered. A total of 374 articles involving people with ID were included. Positive physical fitness outcomes were found in interventions with MPEPs in its morphological components and to a lesser extent in the motor, muscular, metabolic, and cardiorespiratory aspects in people with ID. Further research is needed to standardize and elucidate the effects of the MPEP on other functional dimensions of physical fitness to use them as a physical activity alternative to reduce sedentary behavior in people with I

    Reference Values of Absolute and Relative Handgrip Strength in Chilean Schoolchildren with Intellectual Disabilities

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    Handgrip strength is a simplemeasure of generalmuscle strength and is related to functionality in people with intellectual disabilities. The objective of this research was to describe the normative values of absolute and relative handgrip strength in children, adolescents and adults according to sex. The sample wasmade up of 264 schoolchildren (n = 168men) belonging to five special education schools in Santiago of Chile. The results show higher levels of absolute handgrip strength in males compared to females. The maximum peak of the absolute manual handgrip is reached in females in adolescence with a decrease in adulthood. Relative handgrip strength levels are similar in boys and girls. In females, the relative handgrip strength is similar in childhood and adolescence. Relative handgrip strength declines in both sexes from adolescence to adulthood. The reference values of this study can be used by professionals in the areas of health and education as a guide for interpretation,monitoring and follow-up of Chilean schooled people with intellectual disabilities

    Anthropometric Indicators of the Cardiometabolic Risk, Muscle Strength, and Functional Capacity of Schoolchildren with Intellectual Disabilities during Lockdown in Chile

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    Lockdown due to the COVID-19 pandemic has negatively impacted the social, psychological, and physical well-being of the world population. In the case of people with intellectual disabilities, the impact of lockdown on their physical condition and functionality is not completely clear. This study aimed to determine the effects of COVID-19 lockdown on the anthropometric indicators of cardiometabolic risk, muscle strength, and functionality on schoolchildren with intellectual disabilities. The sample was composed of 132 students of both sexes (n = 74 pre-lockdown; n = 58 lockdown) belonging to two special education centers from the Metropolitan Region of Santiago, Chile. Our results showed significant reductions (p 0.05) in absolute and relative handgrip strength, as well as in functionality, when comparing pre-lockdown and lockdown measurements, with a greater loss in girls than boys. The design and implementation of physical exercise programs centered on strength training are necessary for the physical and functional reconditioning of this population. These programs need to be implemented in special education centers considering the general well-being, quality of life and work needs of people with intellectual disabilities
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