1,996 research outputs found
Ab initio spectroscopic characterization of the radical CHOCH at low temperatures
Spectroscopic and structural properties of methoxymethyl radical
(CHOCH, RDME) are determined using explicitly correlated ab initio
methods. This radical of astrophysical and atmospheric relevance has not been
fully characterized at low temperatures, which has delayed the astrophysical
searches. We provide rovibrational parameters, excitations to the low energy
electronic states, torsional and inversion barriers and low vibrational energy
levels. In the electronic ground state (XA), which appears "clean" from
non-adiabatic effects, the minimum energy structure is an asymmetric geometry
which rotational constants and dipole moment have been determined to be
A=46718.6745 MHz, B=10748.4182 MHz, and C=9272.5105 MHz, and 1.432
D (=0.6952 D, =1.215 D, =0.3016 D), respectively. A
variational procedure has been applied to determine torsion-inversion energy
levels. Each level splits into 3 subcomponents (A/A and E)
corresponding to the three methyl torsion minima. Although the potential energy
surface presents 12 minima, at low temperatures, the infrared band shapes
correspond to a surface with only three minima because the top of the inversion
V barrier at (109 cm) stands below the
zero point vibrational energy and the CH torsional barrier is relatively
high (2000 cm). The methyl torsion barrier was computed to be
500 cm and produces a splitting of 0.01 cm of the ground
vibrational state
High-pressure synthesis of rock salt LiMeO2-ZnO (Me = Fe3+, Ti3+) solid solutions
Metastable LiMeO2-ZnO (Me = Fe3+, Ti3+) solid solutions with rock salt
crystal structure have been synthesized by solid state reaction of ZnO with
LiMeO2 complex oxides at 7.7 GPa and 1350-1450 K. Structure, phase composition,
thermal stability and thermal expansion of the recovered samples have been
studied by X-ray diffraction with synchrotron radiation. At ambient pressure
rock salt LiMeO2-ZnO solid solutions are kinetically stable up to 670-800 K
depending on the composition.Comment: 11 pages, 3 figures, 1 tabl
Evaluation of cleaning and disinfection procedures against Samonella enterica at swine farms, transport and lairage facilities
Evaluation of the cleaning and disinfection protocols effectiveness against Salmonella in three points of the pork production chain: finishing farm, transport and lairage. A 22.2% of the farms, 62.5% of the slaughter trucks and 63.6% of the holding pens tested were positive to Salmonella after cleaning and disinfection procedures
Formation of collective spins in frustrated clusters
Using magnetization, specific heat and neutron scattering measurements, as
well as exact calculations on realistic models, the magnetic properties of the
\lacuvo compound are characterized on a wide temperature range. At high
temperature, this oxide is well described by strongly correlated atomic =1/2
spins while decreasing the temperature it switches to a set of weakly
interacting and randomly distributed entangled pseudo spins and
. These pseudo-spins are built over frustrated clusters, similar to
the kagom\'e building block, at the vertices of a triangular superlattice, the
geometrical frustration intervening then at different scales.Comment: 10 page
Structure of MnO nanoparticles embedded into channel-type matrices
X-ray diffraction experiments were performed on MnO confined in mesoporous
silica SBA-15 and MCM-41 matrices with different channel diameters. The
measured patterns were analyzed by profile analysis and compared to numerical
simulations of the diffraction from confined nanoparticles. From the lineshape
and the specific shift of the diffraction reflections it was shown that the
embedded objects form ribbon-like structures in the SBA-15 matrices with
channels diameters of 47-87 {\AA}, and nanowire-like structures in the MCM-41
matrices with channels diameters of 24-35 {\AA}. In the latter case the
confined nanoparticles appear to be narrower than the channel diameters. The
physical reasons for the two different shapes of the confined nanoparticles are
discussed.Comment: 8 pages, including 9 postscript figures, uses revtex4.cl
CW laser operation around 2-μm in (Tm,Yb):KLu(WO4) 2
Laser generation in continuous wave (CW) regime at 1.94-μm from (Tm,Yb) codoped system has been investigated in two different hosts: KLu(WO 4)2 and KY(WO4)2. The high quality crystals were grown by the Top-Seeded Solution Growth Slow Cooling (TSSG-SC) method with doping levels of 2.5 at. %Tm and 5 at. %Yb. The active media were pumped with a diode laser at 980 nm. We demonstrated the superior performance of KLu(WO4)2 compared to that of KY(WO4) 2 and improved the results already obtained in the literature. The maximum laser output power reached was 157 mW for (Tm,Yb):KLu(WO 4)2 and 123 mW for (Tm,Yb):KY(WO4)2. © 2010 Published by Elsevier Ltd
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CW laser operation around 2-μm in (Tm,Yb):KLu(WO4) 2
Laser generation in continuous wave (CW) regime at 1.94-μm from (Tm,Yb) codoped system has been investigated in two different hosts: KLu(WO 4)2 and KY(WO4)2. The high quality crystals were grown by the Top-Seeded Solution Growth Slow Cooling (TSSG-SC) method with doping levels of 2.5 at. %Tm and 5 at. %Yb. The active media were pumped with a diode laser at 980 nm. We demonstrated the superior performance of KLu(WO4)2 compared to that of KY(WO4) 2 and improved the results already obtained in the literature. The maximum laser output power reached was 157 mW for (Tm,Yb):KLu(WO 4)2 and 123 mW for (Tm,Yb):KY(WO4)2. © 2010 Published by Elsevier Ltd
Inhibition of DNA damage response at telomeres improves the detrimental phenotypes of Hutchinson–Gilford Progeria Syndrome
Hutchinson–Gilford progeria syndrome (HGPS) is a genetic disorder characterized by premature aging features. Cells from HGPS patients express progerin, a truncated form of Lamin A, which perturbs cellular homeostasis leading to nuclear shape alterations, genome instability, heterochromatin loss, telomere dysfunction and premature entry into cellular senescence. Recently, we reported that telomere dysfunction induces the transcription of telomeric non-coding RNAs (tncRNAs) which control the DNA damage response (DDR) at dysfunctional telomeres. Here we show that progerin-induced telomere dysfunction induces the transcription of tncRNAs. Their functional inhibition by sequence-specific telomeric antisense oligonucleotides (tASOs) prevents full DDR activation and premature cellular senescence in various HGPS cell systems, including HGPS patient fibroblasts. We also show in vivo that tASO treatment significantly enhances skin homeostasis and lifespan in a transgenic HGPS mouse model. In summary, our results demonstrate an important role for telomeric DDR activation in HGPS progeroid detrimental phenotypes in vitro and in vivo
Alternativas de manejo expectante de la rotura prematura de membranas antes de la viabilidad en embarazos únicos
La rotura prematura de membranas (RPM) antes de la viabilidad fetal constituye una complicación obstétrica de baja incidencia, pero que se asocia a una alta morbimortalidad materna y perinatal. No existen actualmente guías estandarizadas para el manejo expectante de esta patología, y las prácticas reportadas en la literatura para el enfrentamiento de este escenario clínico son variables. Aquí presentamos una revisión de la literatura de los últimos 10 años y proponemos una pauta de manejo para la RPM antes de la viabilidad basada en la evidencia disponible
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