Comparison Condition Research Articles

Unusually high production of C37:4 alkenone by an Arctic Gephyrocapsa huxleyi strain grown under nutrient-replete conditions

The percentage of C37:4 alkenone relative to total C37 alkenones (C37:4%) in northern high-latitude ocean waters and surface sediments, which can be up to 77%, has been recently found to correlate strongly with annual mean sea ice coverage. Genomic data and culture experiments suggest these high percentage of C37:4 alkenones may be mainly attributed to the production by Group 2i Isochrysidales, because the cosmopolitan Isochrysidales, Emiliania huxleyi (recently renamed to Gephyrocapsa huxleyi) typically does not produce significant amount of C37:4 alkenone in laboratory cultures. However, the presence of significant amounts of C38 methyl alkenones in high-latitude ocean sediments and suspended particulate samples suggests possible contributions from G. huxleyi as well. Here we performed the first culture experiments on G. huxleyi strain NIES3366 from the Chukchi Sea. This strain was isolated from the coldest and highest latitude ocean waters known for G. huxleyi strains so far. NIES1312 from the Bering Sea was also cultured under identical conditions for comparison. We show that, in f/2 growth media, NIES3366 was capable of producing unusually large amounts of C37:4 alkenone reaching 12.8% at 12 °C and up to 20% between 6 °C and 9 °C. In comparison, NIES1312 only produced 3.6% C37:4 at 12 °C. Our results suggest that Arctic strains of G. huxleyi may have also contribute to the inventory of the high-C37:4 alkenone profile in northern high-latitude oceans. Importantly, however, when NIES3366 was grown in 10 times lower nutrient (f/20) at 12 °C, the C37:4% decreased by ∼ 50% (to 6%), indicating a strong impact of nutrients on the production of C37:4 alkenone. In contrast, salinity levels had a negligible impact on the percentage of C37:4 for both strains, indicating an absence of a physiological effect of salinity. We also demonstrate that at low temperatures, tetra-unsaturated alkenones must be included for calculating unsaturation indices to achieve strong linear correlation with temperatures for NIES3366, a feature contrary to other G. huxleyi strains isolated from mid- and low- latitude oceans. Our findings provide a refined mechanistic explanation for the application of alkenone C37:4% as a quantitative sea ice proxy in high-latitude oceans.

Exploring the acute cardiovascular effects of Floatation-REST.

[https://clinicaltrials.gov/show/NCT03051074], identifier [NCT03051074].

The Healthy Kids & Families study: Outcomes of a 24-month childhood obesity prevention intervention

Socioeconomically disadvantaged children experience a high burden of obesity but few interventions address obesity prevention in this population subgroup. The Healthy Kids & Families study tested the effect of a parent-focused community health worker (CHW)-delivered lifestyle intervention to prevent childhood obesity. Participants were child-parent/guardian (Kindergarten to 6th grade at baseline) dyads (n = 247) recruited through schools located in socioeconomically disadvantaged neighborhoods in Worcester, MA, USA. Using a quasi-experimental design, the study tested the impact of Healthy Kids & Families, a theory-based, low-intensity, parent-focused, CHW-delivered intervention to improve children’s weight, healthy eating and physical activity. The attention-control comparison condition was a positive parenting intervention. The primary outcome was change in child body mass index (BMI) z-score at 24 months. Secondary outcomes included number of positive child and parent changes in selected diet and physical activity behaviors targeted by the intervention and change in parent BMI. Outcomes were assessed following the intent-to-treat principle and using multivariable generalized linear mixed models. Compared to the attention-control comparison condition, the Healthy Kids & Families intervention led to a greater reduction in children’s BMI z-score (β = −0.17, 95 %CI: −1.92 to −0.36; p = 0.057) and a greater number of positive behavior changes among children (β = 0.57, 95 %CI: 0.08–1.06; p = 0.02) at 24 months. There was no significant change in parent outcomes. The Healthy Kids & Families intervention shows promise for obesity prevention among children in socioeconomically disadvantaged communities.

A Smartphone-Based Intervention for Anxiety and Depression in Racially and Ethnically Diverse Adults (EASE): Protocol for a Randomized Controlled Trial.

Clear health disparities have emerged in the rates of COVID-19 exposure, hospitalization, and death among Black, Hispanic, and American Indian (BHAI) individuals, relative to non-Hispanic White (NHW) individuals. BHAI populations have been disproportionately affected by lower behavioral health access and heightened negative mental health outcomes during the pandemic. This project directly addresses health disparities in access to behavioral health care during the COVID-19 pandemic among BHAI populations via an adaptation of the established, initially validated, low-cost, mobile app Easing Anxiety Sensitivity for Everyone (EASE) among individuals with symptoms of elevated anxiety or depression or both. The EASE trial is a 2-arm, prospective, randomized, blinded-assessor study with intention-to-treat analysis. Participants (N=800; n=200, 25%, Black; n=200, 25%, Hispanic; n=200, 25%, American Indian; and n=200, 25%, NHW) are randomized to receive either EASE or an active comparison condition for anxiety and depression. Participants compete an online prescreener, an enrollment call to provide informed consent, a baseline survey, a 6-month intervention period, and 3- and 6-month postbaseline assessments. Select participants also complete a 3- and 6-month postbaseline qualitative interview via phone or an online platform (eg, Zoom). Participants complete 2 scheduled daily ecological momentary assessments (EMAs) during the 6-month study period. These twice-daily EMAs guide a just-in-time approach to immediate, personalized behavioral health care. Outcomes include reductions in anxiety and depressive symptoms and functional impairment at 3 and 6 months postrandomization. We also will examine putative mechanisms (eg, anxiety sensitivity [AS] and COVID-19-specific stress and fear) of the intervention effects. Further, as treatment effects may differ across sociocultural factors, perceived discrimination, social support, and socioeconomic status (SES) will be evaluated as potential moderators of treatment effects on the primary outcomes. Process evaluation using data collected during the study, as well as individual interviews with participants, will complement quantitative data. Data from this efficacy trial will determine whether EASE successfully improves symptoms of anxiety and depression and whether these improvements outperform an active comparison control app. If successful, findings from this study have the potential to decrease anxiety and depression symptoms among vulnerable populations determined to be most at risk of exacerbated, long-lasting negative health sequelae. Data from this study may be used to support an implementation and dissemination trial of EASE within real-world behavioral health and social service settings. ClinicalTrials.gov NCT05074693; https://clinicaltrials.gov/ct2/show/NCT05074693. DERR1-10.2196/40713.

Vocabulary Outcomes With Third Graders in a Teacher and Speech-Language Pathologist Collaboration

Purpose: The purpose of this study was to investigate the effects of a vocabulary intervention delivered by teachers collaborating with speech-language pathologists (SLPs) in the classroom as compared with teachers in a noncollaborating condition. Method: This quasi-experimental study employed a collaboration treatment condition ( n = 2 collaborative pairs, n = 34 students) and a comparison condition ( n = 2 noncollaborating teachers, n = 34 students). In both conditions, versions of the Vocabulary Scenario Technique were implemented. Third-grade students completed vocabulary assessments for three vocabulary tasks. Results on each of the measures were analyzed using a two-factor split-plot analysis of variance. Results: A significant interaction effect on the Words-in-Context (WIC) task, with a medium effect size ( f = .28), supported the value-added impact of having the SLP collaborate directly with the teacher in implementing the approach. Gains on the Synonyms and Non-Example measures were not significantly different between the conditions, but large effects were found for all three tasks within the collaboration condition, whereas gains in the comparison condition showed large effects for the Synonyms task only and medium effects for the WIC and Non-Example tasks. Conclusions: SLPs' contributions within their collaborations were associated with gains that were larger than those made by students in classrooms where teachers did not collaborate with SLPs on a vocabulary task requiring application of word meanings in sentences. Clinical implications and areas for future research are discussed.

Interventions for improving executive functions in children with foetal alcohol spectrum disorder (FASD): A systematic review.

Interventions for improving executive functions in children with foetal alcohol spectrum disorder (FASD): A systematic review.

Let's decide what would be convincing, conduct randomized trials with rigorous comparison conditions, and report tests of moderation and publication bias in meta-analyses.

We appreciate Jacobson and colleagues' thoughtful commentary on our meta-review of mobile phone-based interventions for mental health. In this response, we address two issues raised: requiring low to moderate heterogeneity (I2<50%) and requiring no evidence of publication bias for evidence to be classified as "convincing." While we agree these represent a high bar, we disagree that these requirements are destined to fail. Other effect sizes reported in the literature, including effect sizes related to mental health interventions and effect sizes related to mobile health (mHealth) interventions (although not their combination) have met requirements for convincing evidence. Jacobson and colleagues argue that features of the mHealth interventions may produce heterogeneity when meta-analyses combine across intervention types. However, several of the effect sizes we reviewed were based on relatively homogeneous portions of the literature and many of the effect sizes we reviewed showed low to moderate heterogeneity. Ideally, future meta-analyses will examine intervention features as moderators of treatment effects. While an absence of publication bias may be a stringent criterion, all but two of the 34 effect sizes we reviewed did not report formal tests of publication bias. Clearly there is a need to reach consensus on how the strength of evidence for mHealth interventions can be evaluated. From our perspective, convincing evidence will ultimately come from large-scale randomized controlled trials employing rigorous comparison conditions along with meta-analyses that do not combine across control condition types, that examine theoretically important moderators, and report formal tests of publication bias. It is this kind of evidence that the public, clinicians, and the scientific community may need to encourage adoptions of mHealth interventions for mental health treatment and prevention.

Feasibility of an adaptive riding pilot study and acceptability to dementia care partners: “Your spirits are lifted”

ObjectivesWe sought to assess the feasibility and acceptability of an adaptive riding program with dyads (persons living with dementia, family care partners) and a gardening comparison condition. DesignThis is a two-arm (adaptive riding and adaptive gardening), mixed methods, convergent, feasibility study that occurred February 2019-June 2019. InterventionsUpon enrollment, dyads (n=9) self-selected into either community-based adaptive riding (n=5) or adaptive gardening (n=4), two complementary interventions in Northern Colorado. Interventions occurred for hour-long, weekly sessions for eight weeks. Outcome measuresFeasibility was measured with recruitment (actual/planned, response rate, participants enrolled/month) retention, adherence to study procedures (attendance, retention, fidelity), and data collection processes (planned versus collected); and analyzed with descriptive statistics. Acceptability of adaptive riding was measured with pre/post care partner interviews and analyzed using thematic analysis. Afterwards, findings were converged. ResultsWe recruited n=10/24 dyads (6 dyads per month), with the highest response rates for referrals and in-person events, n=9 dyads enrolled. We adhered to study procedures with attendance (6/8 gardening, 8/8 riding), retention (100%), fidelity (100%) and data collected (98%). Care partners (n=5) found the adaptive riding intervention acceptable with two themes Overall hopes: “Joy in the present moment” and “Experience as a Whole: “Your spirits are lifted,” affirming quantitative attendance and retention data. ConclusionFindings underscore the feasibility and acceptability of including care partners of persons living with dementia in complementary interventions involving horsemanship activities. Feasibility data can guide study designs and implementation processes for other nature-based complementary interventions for this population.

Participation in a yoga intervention is associated with improved mental health among Latinx adolescents.

Latinx youth with mental health disorders have worse outcomes when compared to their White (non-Hispanic) counterparts. Latinx youth also have less access to and lower utilization of mental health services. Emerging research supports the psychological and physical benefits of engaging in yoga and yoga may function as a complimentary treatment option for patients with mental health challenges. However, research assessing the efficacy of yoga and mindfulness is particularly sparse among Latinx youth, who may particularly benefit from mind body awareness activities given barriers to more traditional health approaches. The objective of this quasi-experimental study was to examine the effects of a 12-week Vinyasa flow-based yoga group intervention on anxiety, depression, empathy, and life satisfaction among adolescents receiving outpatient mental health treatment. Adolescents (n=186; 12-17years old) were recruited to an active intervention condition (Yoga); a subsequent group of participants (n=91) were recruited in the same manner to an assessment-only comparison control condition (Comparison). The Yoga group participated in culturally and developmentally tailored group yoga classes for 12weeks. Structural equation modelling was used to evaluate the main effect intervention response between participants in the two conditions. At the post-intervention assessment, after controlling for baseline levels of outcome variables (i.e., depression, anxiety, empathy, and life satisfaction), on average participants in the yoga condition reported: less depression symptoms (B=-1.54, p=0.008), less anxiety symptoms (B=-0.75, p=0.048), greater empathy (B=1.32, p=0.025) and greater life satisfaction (B=0.30, p=0.013) as compared to the Comparison condition. Yoga interventions can be an acceptable and feasible modality for promoting well-being and reducing mental health problems among Latinx youth.

The impact of social comparison and (un)fairness on upstream indirect reciprocity: Evidence from ERP

Event-related potential (ERP) technology and the dictator game paradigm are used to explore the formation mechanism of upstream indirect reciprocity behaviors. We design a within subject experiment of 3 (social comparison: upward versus parallel versus downward) × 2 (treatment: fair versus unfair) involving 49 subjects. In the first round of allocations, subjects are forced to accept a monetary amount allocated to them by another player. In the second round, subjects assume the role of allocator and divide a monetary amount between themselves and a third party. Our results show the following: 1) Having received fair treatment from someone else, individuals engaged in downward comparison are more inclined to reciprocate the fairness they had received to a third party compared to individuals in parallel and upward comparison conditions. If individuals receive unfair treatment, they tend to repeat this behavior to a third party regardless of which social comparison condition they are in; 2) Under the condition of upward comparison, individuals receiving unfair treatment exhibit greater FRN amplitude and less P300 amplitude, but in parallel and downward comparison conditions, there is no significance in FRN and P300 amplitude between individuals receiving fair and unfair treatment.

Outcomes of Peer-Provided Individual Placement and Support Services in a Mental Health Peer-Run Vocational Program.

The authors sought to determine whether staff at a peer-run agency could deliver supported employment services with high fidelity to the individual placement and support (IPS) model and whether employment outcomes of peer-delivered IPS plus work-specific health promotion were superior to usual supported employment services. Two teams from a vocational program of a large peer-run agency were studied from July 2015 to July 2017. One team received training and supervision in delivering IPS plus employment-focused physical wellness support and mentoring. The other team continued providing usual supported employment services. Study data included vocational outcomes from 348 clients served by the two teams (IPS, N=184; comparison condition, N=164) and the results of IPS fidelity reviews of the IPS team at study baseline, midpoint, and end. The authors modeled the primary outcome of competitive employment with random-effects logistic regression and adjusted propensity scores for age, gender, race, ethnicity, education, and months of service receipt. Following training, the IPS team demonstrated acceptable and increasing fidelity to the IPS model, achieving "good fidelity" by the end of the 25-month observation period. Among IPS recipients, 43% achieved competitive employment versus 21% of comparison recipients (p<0.001). Multivariable analysis indicated that IPS recipients were significantly more likely to achieve competitive employment than individuals in the comparison group (OR=4.06, p<0.001). Providing training in IPS along with health promotion to the behavioral health peer workforce may help address the severe shortage of IPS services and enhance the competitive employment outcomes of people served by peer-run programs.

Category structure and region-specific selective attention.

A fundamental component of human categorization involves learning to attend selectively to relevant dimensions and ignore irrelevant ones. Past research has shown that humans can learn flexible strategies in which the attended dimensions vary depending on the region of feature space in which classification takes place. However, region-specific selective attention (RSA) is often challenging to learn. Here, we test the hypothesis that RSA is facilitated when individual categories are embedded within single regions of stimulus space rather than dispersed across multiple regions. We conduct an experiment that varies across conditions whether categories are embedded within regions, but in which the same RSA strategy would benefit performance across the conditions. To evaluate the hypothesis, we use measures of overall performance accuracy as well as comparisons among formal computational models that do and do not make allowance for RSA. We find strong support for the hypothesis among the upper-median-performing participants in the tested groups. However, even in the condition that promotes the learning of RSA, performance is considerably worse than in comparison conditions in which a single set of dimensions can be attended throughout the entire stimulus space.

Effects of odors on sleep quality in 139 healthy participants

The present study aimed to systematically examine whether laurinal, orange odor, and a specifically designed “perfume” influence sleep quality. During sleep, healthy participants (n = 139) were presented with odor or no odor through nose clips for fourteen consecutive nights (phase one). We collected physiological parameters together with subjective reports. Later on, longer lasting effects of this manipulation were examined for the following fourteen nights (phase two) without exposition to odors. Additionally, olfactory, cognitive and non-cognitive measures were conducted before phase one, between both phases and after phase two. One-way analyses of variance for repeated measures with nights and condition (1 vs 2) as the within-subject factor and odor condition (0, 1, 2 or 3) together with odor pleasantness rating as between-subject factor, was employed to analyse data. Overall, the present results demonstrated that the odor condition in comparison to control had no consistent effect on sleep in healthy participants which can be possibly explained by exposure to odors via nose clips. However, the analyses indicated that the individual pleasantness of odors enhanced the positive assessment of sleep quality. Altogether, the present results indicate that the subjective perception of an odor’s hedonic value appears to be crucial for sleep quality, not the odors themselves.

Empathy or Escape? Examining Alternative Mechanisms Underlying Responses to Disgust-Evoking Charity Appeals Over Time

Disgust-evoking imagery is often used in charity advertising. Although research suggests disgust has negative effects on prosocial behavior, few studies examine charity appeals. The current two-factor, between-participants experiment compared immediate and delayed responses to disgust versus nondisgust appeals. Immediately following exposure, disgust reduced self-reported message attention and empathy. Yet participants exposed to disgust anticipated greater difficulty forgetting the message, which motivated immediate giving, and they reported thinking about the message more following exposure, which motivated delayed giving. Empathy remained relatively stable under disgust, exceeding the comparison condition over time. Results suggest a nuanced process whereby disgust affects charitable behavior.

Receptive Language Abilities for Females Exposed to Early Life Adversity: Modification by Epigenetic Age Acceleration at Midlife in a 30-Year Prospective Cohort Study.

Deviations from normative trajectories of receptive language abilities following early life adversity (ELA) may indicate an elevated risk for advanced cognitive aging and related morbidities. Accelerated epigenetic aging at midlife may further identify those at greatest risk for advanced cognitive aging following ELA. We examined whether accelerations in epigenetic aging at midlife can identify those individuals who demonstrated the greatest change in receptive language abilities following ELA. Data were drawn from the Female Growth and Development Study (n=86), a 30-year prospective cohort study of females exposed to substantiated child sexual abuse (CSA), a severe ELA, and a non-CSA comparison condition. The Peabody Picture Vocabulary Test-Revised (PPVT-R) measured receptive language abilities on 6 occasions from childhood to mid-life. Interindividual differences in PPVT-R trajectories were examined in relation to CSA exposure and across 5 independent measures of epigenetic age acceleration derived from first (Horvath DNAmAge, Hannum DNAmAge) and second (GrimAge, PhenoAge, Dunedin Pace of Aging) generation epigenetic clocks. Quadratic growth models revealed that PPVT-R scores were significantly lower at age 25 for females exposed to CSA. Specifically, CSA exposed females had lower intercepts when GrimAge was accelerated and a smaller quadratic trend when PhenoAge was accelerated. ELA is associated with significant differences in development of receptive language abilities with the most pronounced differences observed for females with accelerated epigenetic ages at mid-life. These findings suggest that epigenetic age acceleration could serve as an indicator of differences in cognitive aging and portend to later adulthood cognitive functioning.

Missions with Monty: A Game-Based Learning Environment to Promote Comprehension Monitoring and Science Achievement

While game-based learning environments (GBLE) are an increasingly popular means to engage learners, there remains limited research on the benefits of GBLEs for students’ learning and metacognitive skills in classroom contexts. Missions with Monty is a GBLE developed to engage students as they learn comprehension strategies to support their scientific literacy with targeted Next Generation Science Standards content. The current missions focus on ecosystems, earth and human activity, molecules, and organisms. Students navigate through the game to solve challenges that require the application and transfer of science knowledge. One primary and unique focus of Missions with Monty is to benefit students’ metacognition through comprehension monitoring. Comprehension monitoring is an essential strategy to support literacy and is measured through students’ accuracy in rating their performance on comprehension items. In the game, students are explicitly taught and subsequently practice essential comprehension monitoring strategies. Additional key educational outcomes for students playing Missions with Monty include reading achievement, science knowledge, and transfer of science learning.&#x0D; In this study we examined 10 and 11 year old students’ outcomes as they either played the game (n = 144) or learned the content via a computer-based learning environment (CBLE) without game elements in a comparison condition (n = 80) within classrooms of diverse learners in the United States. Significant gains for science learning were found across conditions, (t(223) = 13.67, p &lt;.001). The primary research question of interest focused on whether students who played Missions with Monty were better able to monitor their understanding of science text after playing the game and therefore we compared monitoring, as measured by bias and accuracy, before and after the game play. Effective metacognition is demonstrated by low bias and high accuracy. Findings revealed that both conditions demonstrated improved bias (t(223) = 4.44, p &lt; .001) and accuracy (t(223) = 11.81, p &lt; .001). Thus, students were better able to monitor their science learning through the game, an essential skill for scientific literacy. Future research should continue to examine the benefits of GBLEs versus CBLEs in terms of benefits for motivation and learning.

The impact of fear of losing out (FoLO) on college students' performance goal orientations and learning strategies in Singapore.

The current research investigated the influence of the Fear of Losing Out (FoLO) mindset on learning strategy via performance goal orientation and its interaction with social comparison amongst Singaporean college students. In Study 1, a positive relationship between FoLO and performance goal orientations (i.e., avoidance and approach) was found. Study 2 replicated this finding and further revealed a downstream effect of FoLO on surface learning via performance goal orientations. In addition, social comparison moderated the link between performance goal orientation and surface learning in the mediation model. Specifically, in downward social comparison conditions, FoLO facilitated high performance-avoidance goal orientation, which in turn led to higher surface learning. Comparatively, in upward social comparison conditions, FoLO incited high performance-approach goal orientation, which in turn led to lower surface learning. Taken together, the findings yield significant theoretical and practical implications of FoLO on college students’ goal orientations and learning outcomes.

Machine learning for classification of hypertension subtypes using multi-omics: A multi-centre, retrospective, data-driven study.

SummaryBackgroundArterial hypertension is a major cardiovascular risk factor. Identification of secondary hypertension in its various forms is key to preventing and targeting treatment of cardiovascular complications. Simplified diagnostic tests are urgently required to distinguish primary and secondary hypertension to address the current underdiagnosis of the latter.MethodsThis study uses Machine Learning (ML) to classify subtypes of endocrine hypertension (EHT) in a large cohort of hypertensive patients using multidimensional omics analysis of plasma and urine samples. We measured 409 multi-omics (MOmics) features including plasma miRNAs (PmiRNA: 173), plasma catechol O-methylated metabolites (PMetas: 4), plasma steroids (PSteroids: 16), urinary steroid metabolites (USteroids: 27), and plasma small metabolites (PSmallMB: 189) in primary hypertension (PHT) patients, EHT patients with either primary aldosteronism (PA), pheochromocytoma/functional paraganglioma (PPGL) or Cushing syndrome (CS) and normotensive volunteers (NV). Biomarker discovery involved selection of disease combination, outlier handling, feature reduction, 8 ML classifiers, class balancing and consideration of different age- and sex-based scenarios. Classifications were evaluated using balanced accuracy, sensitivity, specificity, AUC, F1, and Kappa score.FindingsComplete clinical and biological datasets were generated from 307 subjects (PA=113, PPGL=88, CS=41 and PHT=112). The random forest classifier provided ∼92% balanced accuracy (∼11% improvement on the best mono-omics classifier), with 96% specificity and 0.95 AUC to distinguish one of the four conditions in multi-class ALL-ALL comparisons (PPGL vs PA vs CS vs PHT) on an unseen test set, using 57 MOmics features. For discrimination of EHT (PA + PPGL + CS) vs PHT, the simple logistic classifier achieved 0.96 AUC with 90% sensitivity, and ∼86% specificity, using 37 MOmics features. One PmiRNA (hsa-miR-15a-5p) and two PSmallMB (C9 and PC ae C38:1) features were found to be most discriminating for all disease combinations. Overall, the MOmics-based classifiers were able to provide better classification performance in comparison to mono-omics classifiers.InterpretationWe have developed a ML pipeline to distinguish different EHT subtypes from PHT using multi-omics data. This innovative approach to stratification is an advancement towards the development of a diagnostic tool for EHT patients, significantly increasing testing throughput and accelerating administration of appropriate treatment.FundingEuropean Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No. 633983, Clinical Research Priority Program of the University of Zurich for the CRPP HYRENE (to Z.E. and F.B.), and Deutsche Forschungsgemeinschaft (CRC/Transregio 205/1).

Sol—gel approach to low-temperature synthesis of single-phase metastable La2Ga3O7.5 melilite with enhanced grain-boundary oxide ionic conductivity via a kinetically favorable mechanism

Starting with the stoichiometric and highly homogeneous gel-precursor, single-phase metastable melilite La2Ga3O7.5, as the end-member of solid solution La1+xSr1−xGa3O7+x/2 (0≼x≼1), has been synthesized by solid-state reaction at 700 °C for 2 h via a kinetically favorable mechanism and characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), AC impedance spectroscopy, etc. It has been revealed that the as-synthesized melilite La2Ga3O7.5 shows an orthorhombic symmetry with crystal cell parameters a = 11.4690(1) Å, b = 11.2825(4) Å, and c = 10.3735(4) Å, while has more Raman active modes than LaSrGa3O7 with a tetragonal structure, which was also synthesized under the same conditions for comparison, but tends to slowly decompose into perovskite LaGaO3 and Ga2O3 when annealed at 700 °C for over 20 h driven by its meta-stability. Moreover, the metastable La2Ga3O7.5 shows a higher XPS binding energy for the excess oxide ions in the crystal structure than those at normal lattice sites. Its intrinsic grain oxide ion conductivity can reach as high as 0.04 and 0.51 mS·cm−1 at 550 and 700 °C, respectively, characterized by a simple Arrhenius relationship ln(σT)—1/T with invariable activation energy, Ea = 1.22 eV, over the temperature range from 300 to 700 °C, along with an apparent grain boundary conductivity that is about double that from the grains thanks to the clean grain boundaries. This paper provides a new strategic approach to the synthesis of complex oxides that may be of high performance but are difficultly achieved by the conventional ceramic method at high temperatures.

Code-Switching by Spanish–English Bilingual Children in a Code-Switching Conversation Sample: Roles of Language Proficiency, Interlocutor Behavior, and Parent-Reported Code-Switching Experience

Code-switching is a complex bilingual behavior that can be affected by a variety of factors related to characteristics of the speaker, the interlocutor, and the broader sociolinguistic context. A better understanding of these factors is important for interpreting children’s use of code-switching in different elicitation contexts across research studies and in applied settings, such as language sample analysis for clinical assessment. In the current study, we used a conversation sample protocol with a code-switching adult interlocutor to examine the use of English, Spanish, intra-sentential and inter-sentential code-switching, and alignment with the interlocutor by Spanish/English bilingual children with a wide range of language abilities. In a single-language comparison condition, the same examiner engaged the child in conversation using only English or only Spanish. Key findings include that children exhibited limited use of code-switching in the English condition and similar frequency of code-switching in the Spanish, compared to the code-switching, conditions. Children exhibited a tendency to align with the examiner in their use of English vs. Spanish and their use of intra-sentential code-switching during the code-switching context, although they generally code-switched less than the examiner. There was also considerable variability across children. Predictors of this variability included children’s age and language proficiency. However, language proficiency was not associated with the frequency of children’s intra-sentential code-switching in a code-switching context. Parent-report measures of code-switching experience exhibited limited associations with the children’s observed code-switching behavior; inter-sentential switches into English showed the most direct associations. Based on the findings from this exploratory study, we highlight the importance of including a code-switching context when analyzing language samples from bilingual children, considering both the target child and the interlocutor’s behavior, and continuing to refine indirect report measures of code-switching experience.