59 research outputs found
Antisite Disorder-induced Exchange Bias Effect in Multiferroic Y2CoMnO6
Exchange bias effect in the ferromagnetic double perovskite compound
YCoMnO, which is also a multiferroic, is reported. The exchange bias,
observed below 8~K, is explained as arising due to the interface effect between
the ferromagnetic and antiferromagnetic clusters created by {\it antisite}
disorder in this material. Below 8~K, prominent ferromagnetic hysteresis with
metamagnetic "steps" and significant coercive field, 10~kOe are
observed in this compound which has a 75~K. A model based on
growth of ferromagnetic domains overcoming the elastic energy of structurally
pinned magnetic interfaces, which closely resembles martensitic-like
transitions, is adapted to explain the observed effects. The role of {\it
antisite} disorder in creating the domain structure leading to exchange bias
effect is highlighted in the present work.Comment: 4 pages two-column, 4 figures, accepted to Appl. Phys. Let
Spin Freezing in the Spin Liquid Compound FeAl2O4
Spin freezing in the -site spinel FeAlO which is a spin liquid
candidate is studied using remnant magnetization and nonlinear magnetic
susceptibility and isofield cooling and heating protocols. The remnant
magnetization behavior of FeAlO differs significantly from that of a
canonical spin glass which is also supported by analysis of the nonlinear
magnetic susceptibility term . Through the power-law analysis of
, a spin-freezing temperature, = 11.40.9~K and critical
exponent, = 1.480.59 are obtained. Cole-Cole analysis of magnetic
susceptibility shows the presence of broad spin relaxation times in
FeAlO, however, the irreversible dc susceptibility plot discourages an
interpretation based on conventional spin glass features. The magnetization
measured using the cooling-and-heating-in-unequal-fields protocol brings more
insight to the magnetic nature of this frustrated magnet and reveals
unconventional glassy behaviour. Combining our results, we arrive at the
conclusion that the present sample of FeAlO consists of a majority spin
liquid phase with "glassy" regions embedded.Comment: 5 pages, 6 figs, 2-column, Accepted to Phys. Rev.
Ferromagnetism and the Effect of Free Charge Carriers on Electric Polarization in Y_2NiMnO_6 Double Perovskite
The double perovskite Y_2NiMnO_6 displays ferromagnetic transition at Tc = 81
K. The ferromagnetic order at low temperature is confirmed by the saturation
value of magnetization (M_s) and also, validated by the refined ordered
magnetic moment values extracted from neutron powder diffraction data at 10 K.
This way, the dominant Mn4+ and Ni2+ cationic ordering is confirmed. The
cation-ordered P 21/n nuclear structure is revealed by neutron powder
diffraction studies at 300 and 10 K. Analysis of frequency dependent dielectric
constant and equivalent circuit analysis of impedance data takes into account
the bulk contribution to total dielectric constant. This reveals an anomaly
which coincides with the ferromagnetic transition temperature (T_c).
Pyrocurrent measurements register a current flow with onset near Tc and a peak
at 57 K that shifts with temperature ramp rate. The extrinsic nature of the
observed pyrocurrent is established by employing a special protocol
measurement. It is realized that the origin is due to re-orientation of
electric dipoles created by the free charge carriers and not by spontaneous
electric polarization at variance with recently reported magnetism-driven
ferroelectricity in this materialComment: Published in Physical Review
Comparison of Receptive Verbal Abilities Assessed Using the KBIT-2 and BPVS3 in Adults With Down Syndrome
Down syndrome (DS) is the most common genetic cause of intellectual disability. There is, however, considerable variation in cognitive abilities between those with DS, with some individuals scoring at floor on some tests, particularly for age-standardised outcomes. This variation and these floor effects can pose a problem for comparing and combining study populations when different standardised measures have been used to assess individuals’ cognitive abilities, for example combining results across studies to investigate genetic or other factors associated with cognitive abilities. To facilitate this comparison and combination of study populations assessed using different tests of verbal abilities, we administered two commonly used standardised tests of receptive language, the Kaufmann Brief Intelligence Test 2 (KBIT-2) verbal scale and the British Picture Vocabulary Scale 3 (BPVS3) to 34 adults with DS (age range 19–59) to investigate relationships between outcomes for these two tests. We found a very strong correlation between raw scores for the KBIT-2 verbal scale and the BPVS3, and determined equations to convert between scores for the two tests. Intraclass correlations between the two scales for age-equivalents and calculated z scores relative to population norms were also strong, though scores for both outcomes were significantly higher for the KBIT-2 verbal scale compared to the BPVS3. This deviation in scores between the two tests was greater as z scores decreased for both tests (i.e., for lower scoring individuals), with no such relationship observed for age-equivalents. These results indicate the conversion of raw scores between the KBIT-2 verbal scale and the BPVS3 may be a more valid method for the comparison or combination of study samples with DS compared to the use of standardised scores. Such comparisons or combinations will aid our understanding of cognitive variations and factors associated with these variations within the population with DS
Validating the Cognitive Scale for Down Syndrome (CS-DS) to Detect Longitudinal Cognitive Decline in Adults With Down Syndrome
Down syndrome (DS) is associated with intellectual disability and an ultra-high risk of developing dementia. Informant ratings are invaluable to assess abilities and related changes in adults with DS, particularly for those with more severe intellectual disabilities and/or cognitive decline. We previously developed the informant rated Cognitive Scale for Down Syndrome (CS-DS) to measure everyday cognitive abilities across memory, executive function, and language domains in adults with DS, finding CS-DS scores are a valid measure of general abilities, and are significantly lower for those with noticeable cognitive decline compared to those without decline. To further test the validity of the CS-DS in detecting changes associated with cognitive decline we collected longitudinal data across two time points, approximately 1.5–2 years apart, for 48 adults with DS aged 36 years and over. CS-DS total scores (78.83 ± 23.85 vs. 73.83 ± 25.35, p = 0.042) and executive function scores (46.40 ± 13.59 vs. 43.54 ± 13.60, p = 0.048) significantly decreased between the two time points, with scores in the memory domain trending towards a significant decrease (22.19 ± 8.03 vs. 20.81 ± 8.63, p = 0.064). Adults with noticeable cognitive decline at follow-up showed a trend to significantly greater change in total scores (7.81 ± 16.41 vs. 3.59 ± 16.79, p = 0.067) and significantly greater change in executive function scores (5.13 ± 9.22 vs. 1.72 ± 9.97, p = 0.028) compared to those without decline. Change in total scores showed significant correlations with change in scores from other informant measures of everyday adaptive abilities and symptoms associated with dementia, and participant assessment of general cognitive abilities (all p < 0.005), while change in memory scores (R2 = 0.28, p = 0.001) better predicted change in participant cognitive assessment scores than change in executive function (R2 = 0.15, p = 0.016) or language (R2 = 0.15, p = 0.018) scores. These results suggest informants may better detect changes in the executive function domain, while change in informant rated memory scores best predicts change in assessed cognitive ability. Alternatively, memory domain scores may be sensitive to changes across both early and late cognitive decline, whereas executive function domain scores are more sensitive to changes associated with later noticeable cognitive decline. Our results provide further support for the validity of the CS-DS to assess everyday cognitive abilities and to detect associated longitudinal changes in individuals with DS
Predonation Health-Related Quality of Life Scores Predict Time to Recovery in Hematopoietic Stem Cell Donors
AbstractThe physical reactions to hematopoietic stem cell donation have been extensively studied, but less is known about factors that predict poorer donation experiences. The aim of this prospective study was to examine demographic and health-related quality of life (HRQOL) factors that might be associated with recovery and side effects. We also described the changes in HRQOL during the donation process. In total, 275 peripheral blood stem cell (PBSC) and 37 bone marrow (BM) consecutive donors completed the SF-36 questionnaire predonation and 4 weeks, and 3 months postdonation. Predonation HRQOL markers were the strongest predictors of time to recovery. Poorer predonation physical health was associated with longer recovery (P = .017) and certain side effects in PBSC donors. Poorer predonation mental health was associated with longer recovery in BM donors (P = .03) and pain after PBSC donation (P = .003). Physical HRQOL scores declined significantly from predonation to 4 weeks postdonation. This was shown both for PBSC and BM donors (P < .001 and P = .009, respectively), but the decline was much greater for BM donors. There was a return to predonation HRQOL values 3 months after donation in both groups with values well above the mean of the general population (P < .001)
OSVRT NA KNJIGU "MEDIA NOW: UNDERSTANDING MEDIA, CULTURE, AND TECHNOLOGY" NINTH EDITION
Down syndrome (DS) is associated with intellectual disability and an ultra-high risk of developing dementia. Informant ratings are invaluable to assess abilities and related changes in adults with DS, particularly for those with more severe intellectual disabilities and/or cognitive decline. We previously developed the informant rated Cognitive Scale for Down Syndrome (CS-DS) to measure everyday cognitive abilities across memory, executive function, and language domains in adults with DS, finding CS-DS scores are a valid measure of general abilities, and are significantly lower for those with noticeable cognitive decline compared to those without decline. To further test the validity of the CS-DS in detecting changes associated with cognitive decline we collected longitudinal data across two time points, approximately 1.5-2 years apart, for 48 adults with DS aged 36 years and over. CS-DS total scores (78.83±23.85 vs 73.83±25.35, p=0.042) and executive function scores (46.40±13.59 vs 43.54±13.60, p=0.048) significantly decreased between the two time points, with scores in the memory domain trending towards a significant decrease (22.19±8.03 vs 20.81±8.63, p=0.064). Adults with noticeable cognitive decline at follow-up showed a trend to significantly greater change in total scores (7.81±16.41 vs 3.59±16.79, p=0.067) and significantly greater change in executive function scores (5.13±9.22 vs 1.72±9.97, p=0.028) compared to those without decline. Change in total scores showed significant correlations with change in scores from other informant measures of everyday adaptive abilities and symptoms associated with dementia, and participant assessment of general cognitive abilities (all p<0.005), while change in memory scores (R2=0.28, p=0.001) better predicted change in participant cognitive assessment scores than change in executive function (R2=0.15, p=0.016) or language (R2=0.15, p=0.018) scores. These results suggest informants may better detect changes in the executive function domain, while change in informant rated memory scores best predicts change in assessed cognitive ability. Alternatively, memory domain scores may be sensitive to changes across both early and late cognitive decline, whereas executive function domain scores are more sensitive to changes associated with later noticeable cognitive decline. Our results provide further support for the validity of the CS-DS to assess everyday cognitive abilities and to detect associated longitudinal changes in individuals with DS
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