842 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
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
IndexaciĂłn: Web of Science; ScieloLa inclusiĂłn del MLN organometálica = HOC 6 H 4 CH 2 CN • Mo (CO) 5 (6) en sĂlice 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 hĂbridos inorgánicos-orgánicos se piroliza bajo aire a 800 Âş C para dar Ăłxidos nanoestructurados metálicos y / o pirofosfatos de metal (fosfatos) incluidos en las matrices de sĂlice. La morfologĂa de los nanocompuestos monolĂticas 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 nanopartĂculas 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
Higgs-otic Inflation and Moduli Stabilization
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 -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
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 D-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
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 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
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
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
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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