Microscopic evidence for Mn-induced long range magnetic ordering in MAX phase compounds.

Zero and low field nuclear magnetic resonance measurements have been performed on MAX phase samples (Cr1-x Mn x )2AC with A = Ge and Ga in order to obtain local microscopic information on the nature of magnetism in this system. Our results unambiguously provide evidence for the existence of long-range magnetic order in (Cr0.96Mn0.04)2GeC and for (Cr0.93Mn0.07)2GaC, but not for (Cr0.97Mn0.03)2GaC. We point to a possible dependence of long range magnetic order in these MAX phase compounds on the A atom.

Enhanced stability of quantum Hall skyrmions under radio-frequency radiations.

We present in this paper the results from a recent study on the stability of the quantum Hall skyrmions state at a Landau level filling factor (ν) close to ν = 1 in a narrow GaAs quantum well. Consistent with previous work, a resonant behavior is observed in the resistively detected NMR measurements. In the subsequent current-voltage (I-V) measurements to examine its breakdown behavior under radio frequency radiations, we observe that the critical current assumes the largest value right at the 75As nuclear resonant frequency. We discuss possible origin for this unexpectedly enhanced stability.

Perceptions of aging and ageism among Mexican physicians-in-training.

INTRODUCTION: Attributing negative stereotypes to older adults (ageism) may lead to undertreatment, but little is known about the prevalence of ageism among physicians treating patients with cancer in Ibero-America. We studied stereotypes of aging among Mexican physicians-in-training. MATERIALS AND METHODS: Physicians-in-training attending an oncology meeting answered the "Negative Attributes and Positive Potential in Old Age" survey. Ten questions assessed positive characteristics of aging (PPOA; score 1-4, higher scores represent a positive perception), and four assessed negative characteristics (NAOA; score 1-4, higher score representing a negative perception). Descriptive statistics were used to analyze the questionnaires. Participants completed the "Image-of-Aging" question by writing five words describing older adults and young individuals. Each word was rated from - 5 (negative) to + 5 (positive), and presented as word clouds. RESULTS: One hundred physicians-in-training (median age 28.5) were included. For the PPOA scale, the mean score was 2.9 (SD 0.4), while for the NAOA scale it was 2.1 (SD 0.4). Perceptions of aging were better among women and trainees enrolled in geriatrics and/or oncology-related programs. In the "Image-of-Aging" questions, median rating of words describing older adults was - 2, compared to + 3 for young individuals (p < 0.001). Among words used to describe older adults, the most frequent was "frail/frailty" (n = 45), while "health" (n = 46) was the most frequent for younger individuals. CONCLUSIONS: Mexican physicians-in-training showed mostly negative perceptions of aging, exemplified by the use of negative terms to describe older adults. Creating educational initiatives aimed at decreasing ageism among oncology trainees is necessary across Ibero-America.

Cancer and aging in Ibero-America.

Population aging represents a worldwide challenge. In Ibero-America (Spain, Portugal, and the American countries in which the Spanish or Portuguese language are spoken), the number of older adults is growing, leading to an increase in aging-related diseases such as cancer. Older adults already account for half of all cancer cases in Ibero-America, and this proportion will continue to increase. Furthermore, Ibero-American healthcare systems are not adequately prepared to provide care for older adults with cancer, mainly due to a lack of resources and generalized paucity of geriatric training for healthcare providers. Across the region, several clinical initiatives, educational activities and research collaborations have been established to set the foundations of Ibero-American geriatric oncology and to increase the geriatric knowledge among healthcare providers. This article provides an overview of the current landscape of geriatric oncology in Ibero-America, highlighting its critical challenges, opportunities for improvement and collaboration, and future directions.

Charge-density-wave order takes over antiferromagnetism in Bi2Sr2-x La x CuO6 superconductors.

Superconductivity appears in the cuprates when a spin order is destroyed, while the role of charge is less known. Recently, charge density wave (CDW) was found below the superconducting dome in YBa2Cu3O y when a high magnetic field is applied perpendicular to the CuO2 plane, which was suggested to arise from incipient CDW in the vortex cores that becomes overlapped. Here by 63Cu-nuclear magnetic resonance, we report the discovery of CDW induced by an in-plane field, setting in above the dome in single-layered Bi2Sr2-x La x CuO6. The onset temperature T CDW takes over the antiferromagnetic order temperature T N beyond a critical doping level at which superconductivity starts to emerge, and scales with the pseudogap temperature T*. These results provide important insights into the relationship between spin order, CDW and the pseudogap, and their connections to high-temperature superconductivity.

Magnetism and local symmetry breaking in a Mott insulator with strong spin orbit interactions.

Study of the combined effects of strong electronic correlations with spin-orbit coupling (SOC) represents a central issue in quantum materials research. Predicting emergent properties represents a huge theoretical problem since the presence of SOC implies that the spin is not a good quantum number. Existing theories propose the emergence of a multitude of exotic quantum phases, distinguishable by either local point symmetry breaking or local spin expectation values, even in materials with simple cubic crystal structure such as Ba2NaOsO6. Experimental tests of these theories by local probes are highly sought for. Our local measurements designed to concurrently probe spin and orbital/lattice degrees of freedom of Ba2NaOsO6 provide such tests. Here we show that a canted ferromagnetic phase which is preceded by local point symmetry breaking is stabilized at low temperatures, as predicted by quantum theories involving multipolar spin interactions.

Successful Aging, a New Challenge for Developing Countries: The Coyoacán Cohort.

OBJECTIVE: To determine the socio-demographic and health factors associated with a biomedical phenotype of successful aging (SA) among Mexican community-dwelling elderly. DESIGN, SETTING AND PARTICIPANTS: Cross-sectional study of 935 older adults aged 70 or older participating in the Mexican Study of Nutritional and Psychosocial Markers of Frailty. MEASUREMENTS: SA was operationalized in accordance with the phenotype proposed by Rowe and Kahn. Univariate and multivariate logistic regression analyses were carried out in order to identify the correlates of SA. RESULTS: The phenotype of SA was present in 10% of participants. Age (P < 0.001), illiteracy (P = 0.021), polypharmacy (P < 0.001), and physical pain (P < 0.001) were factors independently and inversely associated with the presence of the SA phenotype. The only variable positively associated with SA was good self-perceived health-status (P < 0.001). CONCLUSION: Although age is not modifiable, several other factors associated with SA are. If we are to promote SA, efforts should be made towards improving those modifiable factors negatively associated with its presence, such as pain or polypharmacy. Also, enhancing factors positively associated to it might play a role in improving wellbeing.

Quasiparticle Scattering off Defects and Possible Bound States in Charge-Ordered YBa_{2}Cu_{3}O_{y}.

We report the NMR observation of a skewed distribution of ^{17}O Knight shifts when a magnetic field quenches superconductivity and induces long-range charge-density-wave (CDW) order in YBa_{2}Cu_{3}O_{y}. This distribution is explained by an inhomogeneous pattern of the local density of states N(E_{F}) arising from quasiparticle scattering off, yet unidentified, defects in the CDW state. We argue that the effect is most likely related to the formation of quasiparticle bound states, as is known to occur, under specific circumstances, in some metals and superconductors (but not in the CDW state, in general, except for very few cases in 1D materials). These observations should provide insight into the microscopic nature of the CDW, especially regarding the reconstructed band structure and the sensitivity to disorder.

25-OH-Vitamin D Is Not Associated with Cognitive Performance among Mexican Community-Dwelling Older Persons.

BACKGROUND: Low cognitive performance has been associated with a wide array of adverse health-related outcomes in elderly populations. Recently, the effect of vitamin D on cognition has been studied; however, its benefits are still controversial. Moreover, most studies have been carried out on North-American and European populations where vitamin D deficiency could represent a greater public-health issue when compared to Latin American ones. OBJECTIVE: To investigate the association between 25-OH-vitamin D and cognitive performance in Mexican community-dwelling elderly. DESIGN, SETTING AND PARTICIPANTS: Cross-sectional study sample of 331 community-dwelling elderly aged 70 and older, participating in the Mexican Study of Nutritional and Psychosocial Markers of Frailty. MEASUREMENTS: Serum 25-OH-vitamin D, cognitive performance as per the Mini-Mental State Examination (MMSE) and the IST (Isaacs Set Test), as well as several elements from the comprehensive geriatric assessment. RESULTS: Mean age of participants was 79.3 years (SD 5.9), 54.1% were women. The mean serum 25-OH-vitamin D level was 59.0 (SD 23.3) nmol/L while mean MMSE score was 22.3 (SD 3.4) and mean IST score was 37.1 (SD 9.1). Although 25-OH-vitamin D levels were lower across all the definitions of low cognitive perfomance, the difference between groups was not statistically significant in any of them. CONCLUSION: No association between 25-OH-vitamin D level and cognitive performance was found in this population of Mexican community-dwelling elderly. Further investigation is required in order to clarify its existence and if so, to delineate its characteristics.

Superconducting anisotropy in the electron-doped high-Tc superconductors Pr2-xCexCuO4-y.

We report superconducting anisotropy measurements in the electron-doped high-Tc superconductors (HTSCs) Pr(2-x)Ce(x)C(u)O(4-y) (PCCO, x = 0.15 and 0.17) with an applied magnetic field (H0) up to 28 T. Our results show that the upper critical field [H(c2)(T)] of PCCO is highly anisotropic and as the temperature T → 0, the value of it at H0 ∥ c [H(c2,∥c)(0)] is far less than the Pauli limit. The low temperature anisotropic character of PCCO is found to be rather similar to that of hole-doped cuprate HTSCs, but apparently larger than that of typical Fe-based superconductors. This study also proves a new sensitive probe of detecting rich properties of unconventional superconductors with the use of the resonant frequency of an NMR probe circuit.

Emergent antiferromagnetism out of the "hidden-order" state in URu2Si2: high magnetic field nuclear magnetic resonance to 40 T.

Very high field (29)Si-NMR measurements using a fully (29)Si-enriched URu(2)Si(2) single crystal were carried out in order to microscopically investigate the "hidden order" (HO) state and adjacent magnetic phases in the high field limit. At the lowest measured temperature of 0.4 K, a clear anomaly reflecting a Fermi surface instability near 22 T inside the HO state is detected by the (29)Si shift, (29)K(c). Moreover, a strong enhancement of (29)K(c) develops near a critical field H(c) ≃ 35.6 T, and the ^{29}Si-NMR signal disappears suddenly at H(c), indicating the total suppression of the HO state. Nevertheless, a weak and shifted (29)Si-NMR signal reappears for fields higher than H(c) at 4.2 K, providing evidence for a magnetic structure within the magnetic phase caused by the Ising-type anisotropy of the uranium ordered moments.

Frailty Is Associated with Disability and Recent Hospitalization in Community-Dwelling Elderly: The Coyoacan Cohort.

BACKGROUND: The phenotype of frailty proposed by Fried et al has shown to predict several adverse health-related outcomes in elderly populations worldwide; however, the description of such associations in Latin America is still scarce. OBJECTIVE: To describe the association between frailty and recent hospitalization, disability for basic (ADL) and instrumental activities of daily living (IADL). DESIGN, SETTING AND PARTICIPANTS: Cross-sectional study of 1,124 community-dwelling adults aged 70 and older participating in the Coyoacán cohort. MEASUREMENTS: Frailty was defined by the presence of at least three of the following criteria: weight loss, exhaustion, low physical activity, slowness, and weakness. Multiple regression analyses were used to test the association between frailty and the outcomes of interest, adjusting for potential confounders. RESULTS: Mean age was 78.2 (SD ±6.1) years. Prevalence of frailty was 14.1%. Adjusted multivariate models showed that frail status was associated with ADL disability (OR 3.06, 95%CI 1.52-6.17), IADL disability (OR 17.02, 95%CI 6.16-47.01), and recent hospitalization (OR 3.21, 95%CI 1.31-7.8). CONCLUSION: Among Mexican community-dwelling elderly, frailty is associated with ADL and IADL disability as well as with recent hospitalizations. Moreover, frailty's prevalence in this population appears to be greater compared to what has been reported elsewhere. Social and cultural traits should be further studied as correlates of frailty in diverse populations.

Molecular Crossroads of Frailty and HIV.

An epidemiological transition is occurring regarding Human Immunodeficiency Virus (HIV) infection. This phenomenon, explained by several mechanisms (e.g.: physiologic changes, pharmacologic advances, sexual behaviors), is demonstrated by a significant increase in the number of patients aged 50 years and older diagnosed with this infection. The immunological changes observed in HIV-infected patients may prompt the appearance of an accelerated aging process as well as that of comorbidities and other pathological entities commonly diagnosed in older adults. Frailty is a biologic syndrome characterized by a multi-systemic decrease of the individual's physiologic and homeostatic reserves, leading to diminished resistance against stressors and increased vulnerability. The purpose of this review is to describe the common molecular changes seen in both frailty and HIV-1 infection, offering an in-depth analysis of their pathophysiology and specifying common processes where their pathways meet.

Association between Self-Reported Health Status and Frailty in Community-Dwelling Elderly.

BACKGROUND: The phenotype of frailty proposed by Fried et al. has been related with increased vulnerability for the development of adverse health-related outcomes. However, this phenotype is not often used in daily clinical practice. On the other hand, poor self-reported health status (SRHS) has been associated with similar adverse health-related outcomes. OBJECTIVES: To determine the association between poor SRHS and frailty. DESIGN, SETTING AND PARTICIPANTS: Cross-sectional study of 927 community-dwelling elderly aged 70 and older, participating in the Mexican Study of Nutritional and Psychosocial Markers of Frailty. MEASUREMENTS: SRHS was established by the question "How do you rate your health status in general?" Frailty was defined according to the phenotype proposed by Fried et al. The association between SRHS and frailty was determined through the construction of multinomial logistic regression models. Final analyses were adjusted by socio-demographic and health covariates, including depressive symptoms. Also, agreement between SRHS and the phenotype of frailty was explored. RESULTS: Prevalence of frailty was 14.1%, and 4.4% of participants rated their health status as "poor". The unadjusted regression analyses demonstrated that fair and poor SRHS were significantly associated with prefrail and frail status. After adjustment for multiple covariates, the association remained statistically significant. However, in the final adjustment for depressive symptoms, only the association between poor SRHS and frail status continued to be statistically significant. Fair agreement between poor SRHS and frail status was also found. CONCLUSION: Poor SRHS shares common correlates as well as health-related adverse outcomes with frailty syndrome, and remains associated with it even when possible confounders are taken into account. Therefore, poor SRHS could be further explored as an option for frailty syndrome screening.

Absence of static loop-current magnetism at the apical oxygen site in HgBa2CuO4+δ from NMR.

The simple structure of HgBa(2)CuO(4+δ) (Hg1201) is ideal among cuprates for study of the pseudogap phase as a broken symmetry state. We have performed (17)O nuclear magnetic resonance on an underdoped Hg1201 crystal with a transition temperature of 74 K to look for circulating loop currents proposed theoretically and inferred from neutron scattering. The narrow spectra preclude static local fields in the pseudogap phase at the apical site, suggesting that the moments observed with neutrons are fluctuating. The nuclear magnetic resonance frequency shifts are consistent with a dipolar field from the Cu(2+) site.

The Phenotype of Frailty and Health-Related Quality of Life.

BACKGROUND: Frailty is a multidimensional problem in the elderly, but there is little information about its implications on health-related quality of life (HRQoL). OBJECTIVES: To determine the association between frailty and HRQoL as well as the association between each component of the phenotype of frailty and the physical (PCS) and mental (MCS) components summaries of QoL. DESIGN, SETTING AND PARTICIPANTS: Cross-sectional study of 496 community-dwelling elderly aged 70 and older, participating in the Mexican Study of Nutritional and Psychosocial Markers of Frailty. MEASUREMENTS: Frailty was defined by the presence of at least three of the following criteria: weight loss, exhaustion, low physical activity, slowness, and weakness. QoL and both of its components were assessed through the SF-36. The association of each component of frailty with the PCS and the MCS of QoL was determined through the construction of multivariate lineal regression models. Final analyses were adjusted by socio-demographic characteristics and by the remaining four components of frailty as covariates. RESULTS: Mean age of participants was 78.0 (SD ± 6.2), 49.4% were women, and 12.7% were frail. Multivariate lineal regression analysis showed that frail and prefrail participants had lower scores for the PCS (P < .001) and the MCS (P < .001) of QoL in comparison with non-frail subjects. Weight loss (P < .001) and exhaustion (P < .001) had an independent inverse association with the MCS of QoL while gait speed (P < .001) and grip strength (P < .001) were also inversely associated with the PCS score. CONCLUSION: Frailty is independently associated with lower scores in the MCS and the PCS of QoL. The finding that different components of frailty were associated with both dimensions of QoL reflects the need for individualized treatment of frail elderly.

Spin-density wave near the vortex cores in the high-temperature superconductor Bi2Sr2CaCu2O8+y.

Competition with magnetism is at the heart of high-temperature superconductivity, most intensely felt near a vortex core. To investigate vortex magnetism we have developed a spatially resolved probe based upon NMR spin-lattice-relaxation spectroscopy. With this approach we have found a spin-density wave associated with the vortex core in Bi(2)Sr(2)CaCu(2)O(8+y), similar to checkerboard patterns in the local density of electronic states reported from scanning tunneling microscope experiments. We have determined both the spin-modulation amplitude and decay length from the vortex core in fields up to H=30 T.

Distinct high-T transitions in underdoped Ba(1-x)KxFe2As2.

In contrast with the simultaneous structural and magnetic first order phase transition T0 previously reported, our detailed investigation on an underdoped Ba(0.84)K(0.16)Fe2As2 single crystal unambiguously revealed that the transitions are not concomitant. The tetragonal (τ: I4/mmm)-orthorhombic (ϑ: Fmmm) structural transition occurs at T(S)≃110 K, followed by an adjacent long-range antiferromagnetic (AFM) transition at T(N)≃102 K. Hysteresis and coexistence of the τ and ϑ phases over a finite temperature range observed by NMR experiments confirm the first order character of the τ-ϑ transition and provide evidence that both T(S) and T(N) are strongly correlated. Our data also show that superconductivity develops in the ϑ phase below T(c)=20 K and coexists with AFM. This new observation, T(S)≠T(N), firmly establishes another similarity between the hole-doped BaFe2As2 and the electron-doped iron-arsenide superconductors.

77Se and 63Cu NMR studies of the electronic correlations in CuxTiSe2 (x = 0.05, 0.07).

We report a (77)Se and (63)Cu nuclear magnetic resonance (NMR) investigation on the charge-density-wave (CDW) superconductor Cu(x)TiSe(2) (x = 0.05 and 0.07). At high magnetic fields where superconductivity is suppressed, the temperature dependence of (77)Se and (63)Cu spin-lattice relaxation rates 1/T(1) follow a linear relation. The slope of (77)Se 1/T(1) versus T increases with the Cu doping. This can be described by a modified Korringa relation which suggests the significance of electronic correlations and the Se 4p- and Ti 3d-band contribution to the density of states at the Fermi level in the studied compounds.

Chemical pressure induced spin freezing phase transition in kagome pr langasites.

The 2D kagome system Pr3Ga5SiO14 has been previously identified as a spin-liquid candidate in zero field, displaying no magnetic long-ranged order down to at least 35 mK. Perturbations upon such systems, either under applied fields or applied pressure, should induce a spin freezing phase transition, but there are very few experimental realizations of this phenomena other than the well-studied 3D pyrochlore Tb2Ti2O7. In this Letter, we report the observation of a spin freezing phase transition in Pr3Ga5SiO14 through the application of chemical pressure--that is, through a systematic substitution on the Si site with larger ions and an elongation of the nearest-neighbor Pr-Pr distance in the kagome lattice. This results in a suppression of the T2 component of the heat capacity, and the reduction of the exchange constant eventually leads to dipolar-driven spin freezing.