Phase diagram and magnetic properties of La1−x_{1-x}Cax_xMnO3_3 compound for 0≤x≤0.230\leq x \leq 0.23

In this article a detailed study of La$_{1-x}$Ca$_x$MnO$_3$ ($0\leq x \leq 0.23$) phase diagram using powder x-ray diffraction and magnetization measurements is presented. Unfortunately, in the related literature no properly characterized samples have been used, with consequence the smearing of the real physics in this complicated system. As the present results reveal, there are two families of samples. The first family concerns samples prepared in atmosphere ($P({\rm O}_2)=0.2$ Atm) which are all ferromagnetic with Curie temperature rising with $x$. The second family concerns samples, where a post annealing in nearly zero oxygen partial pressure is applied. These samples show a canted antiferromagnetic structure for $0\leq x \leq 0.1$ below $T_N$, while for $0.125\leq x <0.23$ an unconventional ferromagnetic insulated phase is present below $T_c$. The most important difference between nonstoichiometric and stoichiometric samples concerning the magnetic behavior, is the anisotropy in the exchange interactions, in the stoichiometric samples putting forward the idea that a new orbital ordered phase is responsible for the ferromagnetic insulating regime in the La$_{1-x}$Ca$_x$MnO$_3$ compound

Degeneracy in excited state quantum phase transitions of two-level bosonic models and its influence on system dynamics

Excited state quantum phase transitions in collective many-body quantum systems influence the system spectral properties due to changing degeneracy patterns in different phases. We report a fundamental difference in the nature of the degeneracy for boson two-level models, depending on the dimension of the space where the models were defined. To illustrate the consequences, we assess the validity of an out-of-time-order correlator as a possible order operator for excited state quantum phase transitions in different models

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

Evidence for Jahn-Teller distortions at the antiferromagnetic transition in LaTiO3_3

LaTiO$_3$ is known as Mott-insulator which orders antiferromagnetically at $T_{\rm N}=146$ K. We report on results of thermal expansion and temperature dependent x-ray diffraction together with measurements of the heat capacity, electrical transport measurements, and optical spectroscopy in untwinned single crystals. At $T_{\rm N}$ significant structural changes appear, which are volume conserving. Concomitant anomalies are also observed in the dc-resistivity, in bulk modulus, and optical reflectivity spectra. We interpret these experimental observations as evidence of orbital order.Comment: 4 pages, 4 figures; published in Phys. Rev. Lett. 91, 066403 (2003

Utility of Masson’s Trichrome Stain in the Quantification of Mean Vascular Density in Normal Oral Mucosa, Epithelial Dysplasia and Oral Squamous Cell Carcinoma

Indexación: Scopus; Scielo.El objetivo de este estudio fue valuar la utilidad del uso de la tinción de Tricrómico de Masson (TM) en la cuantificación de la densidad media vascular (DMV) en Mucosa Oral Normal (MON), Displasia Epitelial Oral (DEO) y Carcinoma Oral de Células Escamosas (COCE). Estudio descriptivo de serie de casos. Se analizaron 17 muestras de MON, 15 muestras de DEO y 16 de COCE, teñidas con TM. Para determinar su utilidad, se compararon con las mismas muestras analizadas con técnica de inmunohistoquímica contra CD31. La cuantificación de la DMV se realizó en las 3 áreas de mayor vascularización de cada muestra. Se determinó la DMV según diagnóstico mediante la tinción TM e inmunohistoquímica contra CD31, y se calculó la correlación entre ambos. La DMV cuantificada con TM y contra CD31 difiere según el diagnóstico, observándose un aumento de la DMV al malignizarse el diagnóstico. No se encontraron diferencias al comparar la DMV cuantificada con TM y contra CD31. La correlación de la DMV analizado por TM y contra CD31 es significativa y moderada. La cuantificación de vasos sanguíneos es posible mediante la tinción de TM en muestras de MON, DEO y COCE, con una correlación moderada con la inmunohistoquímica contra CD31.The objective of this study was to evaluate the utility of Masson's Trichrome (TM) staining in the quantification of the mean vascular density (DMV) in samples of normal oral mucosa (MON), oral epithelial dysplasia (ODE) and oral squamous cell carcinoma (COCE). The design - a descriptive study of case series. We analyzed 17 samples of MON, 15 samples of DEO and 16 samples of COCE, stained with TM. To determine usefulness, we compared and analyzed the same samples, either stained with TM or with immunohistochemical technique against CD31. Quantification of the DMV was performed in the 3 areas of greatest vascularization in each sample. DMV was determined according to diagnosis by TM staining and immunohistochemistry against CD31, and the correlation between the two was then calculated. DMV quantified with TM and against CD31 differs according to the diagnosis, with an increase in DMV upon malignant diagnosis. No differences were found when comparing DMV quantified with TM and against CD31. The correlation of the DMV analyzed by TM and against CD31 is significant and moderate. Quantification of blood vessels is possible by TM staining in samples of MON, DEO and COCE. TM staining is moderately correlated with immunohistochemistry against CD31.https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0717-95022017000401576&lng=en&nrm=iso&tlng=e

Crystal structure and high-field magnetism of La2CuO4

Neutron diffraction was used to determine the crystal structure and magnetic ordering pattern of a La2CuO4 single crystal, with and without applied magnetic field. A previously unreported, subtle monoclinic distortion of the crystal structure away from the orthorhombic space group Bmab was detected. The distortion is also present in lightly Sr-doped crystals. A refinement of the crystal structure shows that the deviation from orthorhombic symmetry is predominantly determined by displacements of the apical oxygen atoms. An in-plane magnetic field is observed to drive a continuous reorientation of the copper spins from the orthorhombic b-axis to the c-axis, directly confirming predictions based on prior magnetoresistance and Raman scattering experiments. A spin-flop transition induced by a c-axis oriented field previously reported for non-stoichiometric La2CuO4 is also observed, but the transition field (11.5 T) is significantly larger than that in the previous work

Magnetic order and multipole interactions in CexPr1-xB6 solid solutions

Magnetic ordering phenomena in CexPr1-xB6 solid solutions have been studied using both powder and single-crystal neutron diffraction. A variety of magnetic structures are observed depending on temperature and Ce concentration. Over a broad composition range (x $\le$ 0.7), Pr-Pr interactions play a dominant role, giving rise to incommensurate structures with wave vectors of the form k{IC1}=(1/4-delta, 1/4, 1/2) or k{IC2}=(1/4-delta, 1/4-delta, 1/2). The crossover to a CeB6-like regime takes place near x = 0.7-0.8. For the latter composition, the antiferroquadrupolar phase transition observed in transport measurements precedes the onset, at lower temperature, of a commensurate magnetic order similar to that existing in CeB6. However, unlike in the pure compound, an incommensurate magnetic order is formed at even higher temperature and persists in the antiferroquadrupolar phase down to the lock-in transition. These results are shown to reflect the interplay between various type of dipole exchange and higher multipole interactions in this series of compounds.Comment: Abstract of submission changed to get rid of LaTeX code Minor differences exist between this version and that published in PRB (corrections introduced by publisher