MDPI Collection

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12588/185

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Green Leaf Volatiles: A New Player in the Protection against Abiotic Stresses?
(2024-08-30) Engelberth, Jurgen
To date, the role of green leaf volatiles (GLVs) has been mainly constrained to protecting plants against pests and pathogens. However, increasing evidence suggests that among the stresses that can significantly harm plants, GLVs can also provide significant protection against heat, cold, drought, light, and salinity stress. But while the molecular basis for this protection is still largely unknown, it seems obvious that a common theme in the way GLVs work is that most, if not all, of these stresses are associated with physical damage to the plants, which, in turn, is the major event responsible for the production of GLVs. Here, I summarize the current state of knowledge on GLVs and abiotic stresses and provide a model explaining the multifunctionality of these compounds.
Characterization of Trabecular Bone Microarchitecture and Mechanical Properties Using Bone Surface Curvature Distributions
(2024-08-22) Xiao, Pengwei; Schilling, Caroline; Wang, Xiaodu
Understanding bone surface curvatures is crucial for the advancement of bone material design, as these curvatures play a significant role in the mechanical behavior and functionality of bone structures. Previous studies have demonstrated that bone surface curvature distributions could be used to characterize bone geometry and have been proposed as key parameters for biomimetic microstructure design and optimization. However, understanding of how bone surface curvature distributions correlate with bone microstructure and mechanical properties remains limited. This study hypothesized that bone surface curvature distributions could be used to predict the microstructure as well as mechanical properties of trabecular bone. To test the hypothesis, a convolutional neural network (CNN) model was trained and validated to predict the histomorphometric parameters (e.g., BV/TV, BS, Tb.Th, DA, Conn.D, and SMI), geometric parameters (e.g., plate area PA, plate thickness PT, rod length RL, rod diameter RD, plate-to-plate nearest neighbor distance NND_PP, rod-to-rod nearest neighbor distance NND_RR, plate number PN, and rod number RN), as well as the apparent stiffness tensor of trabecular bone using various bone surface curvature distributions, including maximum principal curvature distribution, minimum principal curvature distribution, Gaussian curvature distribution, and mean curvature distribution. The results showed that the surface curvature distribution-based deep learning model achieved high fidelity in predicting the major histomorphometric parameters and geometric parameters as well as the stiffness tenor of trabecular bone, thus supporting the hypothesis of this study. The findings of this study underscore the importance of incorporating bone surface curvature analysis in the design of synthetic bone materials and implants.
Updates on Mechanisms of Cytochrome P450 Catalysis of Complex Steroid Oxidations
(2024-08-20) Guengerich, F. Peter; Tateishi, Yasuhiro; McCarty, Kevin D.; Yoshimoto, Francis K.
Cytochrome P450 (P450) enzymes dominate steroid metabolism. In general, the simple C-hydroxylation reactions are mechanistically straightforward and are generally agreed to involve a perferryl oxygen species (formally FeO³⁺). Several of the steroid transformations are more complex and involve C-C bond scission. We initiated mechanistic studies with several of these (i.e., 11A1, 17A1, 19A1, and 51A1) and have now established that the dominant modes of catalysis for P450s 19A1 and 51A1 involve a ferric peroxide anion (i.e., Fe³⁺O₂¯) instead of a perferryl ion complex (FeO³⁺), as demonstrated with ¹⁸O incorporation studies. P450 17A1 is less clear. The indicated P450 reactions all involve sequential oxidations, and we have explored the processivity of these multi-step reactions. P450 19A1 is distributive, i.e., intermediate products dissociate and reassociate, but P450s 11A1 and 51A1 are highly processive. P450 17A1 shows intermediate processivity, as expected from the release of 17-hydroxysteroids for the biosynthesis of key molecules, and P450 19A1 is very distributive. P450 11B2 catalyzes a processive multi-step oxidation process with the complexity of a chemical closure of an intermediate to a locked lactol form.
Cardiometabolic Risk Factors Associated with Magnesium and Vitamin D Nutrients during Pregnancy—A Narrative Review
(2024-08-09) Naowar, Maisha; Dickton, Darby; Francis, Jimi
This narrative review comprehensively explores the cardiometabolic implications of two vital nutrients, magnesium and vitamin D, during gestation. Magnesium, a key regulator of vascular tone, glucose metabolism, and insulin sensitivity, plays a crucial role in mitigating gestational hypertension and diabetes, a point this review underscores. Conversely, vitamin D, critical for immune response and calcium level maintenance, is linked to gestational diabetes and hypertensive disorders of pregnancy. The authors aim to enhance comprehension of the complex interaction between these nutrients and cardiometabolic function in pregnancy, knowledge that is pivotal for optimizing maternal–fetal outcomes. The mother’s health during pregnancy significantly influences the long-term development of the fetus. Recognizing the impact of these nutrient deficiencies on the physiology of cardiometabolic cycles underscores the importance of adequate nutritional support during pregnancy. It also emphasizes the pressing need for future research and targeted interventions to alleviate the burden of pregnancy complications, highlighting the crucial role of healthcare professionals, researchers, and policy makers in obstetrics and gynecology in this endeavor.
Non-Debye Behavior of the Néel and Brown Relaxation in Interacting Magnetic Nanoparticle Ensembles
(2024-08-09) Botez, Cristian E.; Knoop, Jeffrey
We used ac-susceptibility measurements to study the superspin relaxation in Fe₃O₄/Isopar M nanomagnetic fluids of different concentrations. Temperature-resolved data collected at different frequencies, χ″ vs. T|_f, reveal magnetic events both below and above the freezing point of the carrier fluid (T_F = 197 K): χ″ shows peaks at temperatures T_p1 and T_p2 around 75 K and 225 K, respectively. Below T_F, the Néel mechanism is entirely responsible for the superspin relaxation (as the carrier fluid is frozen), and we found that the temperature dependence of the relaxation time, τ_N(T_p1), is well described by the Dorman–Bessais–Fiorani (DBF) model: τNT=τrexp⁡EB+EadkB T. Above T_F, both the internal (Néel) and the Brownian superspin relaxation mechanisms are active. Yet, we found evidence that the effective relaxation times, τ_eff, corresponding to the T_p2 peaks observed in the denser samples do not follow the typical Debye behavior described by the Rosensweig formula 1τeff=1τN+1τB. First, τ_eff is 5 × 10⁻⁵ s at 225 K, almost three orders of magnitude more that its Néel counterpart, τ_N~8 × 10⁻⁸ s, estimated by extrapolating the above-mentioned DBF analysis. Thus, 1τN≫1τeff, which is clearly not consistent with the Rosensweig formula. Second, the observed temperature dependence of the effective relaxation time, τ_eff(T_p2), is excellently described by τB−1T=Tγ0exp⁡−E′kBT−T0′, a model solely based on the hydrodynamic Brown relaxation, τB(T)=3ηTVHkBT, combined with an activation law for the temperature variation of the viscosity, ηT=η0exp⁡E′/kB(T−T0′. The best fit yields γ0=3ηVHkB = 1.6 × 10⁻⁵ s·K, E′/k_B = 312 K, and T₀′ = 178 K. Finally, the higher temperature T_p2 peaks vanish in the more diluted samples (δ ≤ 0.02). This indicates that the formation of larger hydrodynamic particles via aggregation, which is responsible for the observed Brownian relaxation in dense samples, is inhibited by dilution. Our findings, corroborating previous results from Monte Carlo calculations, are important because they might lead to new strategies to synthesize functional magnetic ferrofluids for biomedical applications.
Experimental Benchmarking of Existing Offline Parameter Estimation Methods for Induction Motor Vector Control
(2024-08-01) Reddy, Butukuri Koti; Ayyagari, Krishna Sandeep; Kumar, Yemula Pradeep; Giri, Nimay Chandra; Rajgopal, Panganamamula Venkata; Fotis, Georgios; Mladenov, Valeri
Induction motors dominate industrial applications due to their unwavering reliability. However, optimal vector control, critical for maximizing dynamic performance, hinges on accurate parameter estimation. This control strategy necessitates precise knowledge of the motor’s parameters, obtainable through experimentation or calculation based on its design specifications. Numerous methods, ranging from traditional to computational, have been proposed by various researchers, often relying on specific assumptions that might compromise the performance of modern motor control techniques. This paper meticulously reviews the most frequently utilized methods and presents experimental results from a single motor. We rigorously compare these results against established benchmark methods, including IEEE Standard 112-2017, and subsequently identify the superior approach, boasting a maximum error of only 6.5% compared to 19.65% for competing methods. Our study investigates the parameter estimation of induction motor. The methodology primarily utilizes RMS values for measurement tasks. Moreover, the impact of harmonics, particularly when an induction motor is supplied by an inverter is briefly addressed. The pioneering contribution of this work lies in pinpointing a more accurate parameter estimation method for enhanced vector control performance. These findings pave the way for exceptional vector control, particularly at lower speeds, ultimately elevating both vector control and drive performance.
The Influence of Proximity on the Evolution of Urban Innovation Networks in Nanjing Metropolitan Area, China: A Comparative Analysis of Knowledge and Technological Innovations
(2024-08-01) Shi, Yu; Zhai, Wei; Yan, Yiran; Wang, Xingping
This study investigates the dynamics of innovation element flows among metropolitan areas and examines the underlying proximity mechanisms that are crucial for elevating urban agglomerations’ innovation levels and spurring their development. Utilizing collaborative publication and patent data, this research constructs knowledge and technological innovation networks within the Nanjing metropolitan area (NMA) from 2013 to 2020. It analyzes the evolution of network structures and applies the Multiple Regression Quadratic Assignment Procedure to discern the proximity mechanisms driving the urban innovation networks’ evolution in NMA. The main findings are as follows: (1) The knowledge collaborations within NMA cities remain largely confined to cities within Jiangsu province, whereas the technological collaborations are shifting from intra-province to cross-province cooperation. (2) Both knowledge and technological innovation networks display a “core-periphery” configuration, with Nanjing maintaining a dominant central position. The scale of the KIN surpasses that of the TIN, while the latter’s growth rate outpaces the former’s. Technological collaborations demonstrate more pronounced spillover effects than their knowledge counterparts. (3) At the metropolitan area level, organizational, social, cognitive, and technological proximities exert varying degrees of influence on innovation cooperation among different innovation entities across various years. Cognitive proximity exhibits the most substantial explanatory power. Based on these findings, the study proposes relevant policy recommendations for constructing an innovative NMA and promoting collaborative innovation development among cities within the NMA.
Quantum Laplace Transforms for the Ulam–Hyers Stability of Certain q-Difference Equations of the Caputo-like Type
(2024-07-28) Etemad, Sina; Stamova, Ivanka; Ntouyas, Sotiris K.; Tariboon, Jessada
We aim to investigate the stability property for the certain linear and nonlinear fractional q-difference equations in the Ulam–Hyers and Ulam–Hyers–Rassias sense. To achieve this goal, we prove that three types of the linear q-difference equations of the q-Caputo-like type are Ulam–Hyers stable by using the quantum Laplace transform and quantum Mittag–Leffler function. Moreover, after proving the existence property for a nonlinear Cauchy q-difference initial value problem, we use the same quantum Laplace transform and the q-Gronwall inequality to show that it is generalized Ulam–Hyers–Rassias stable.
Without My Family, I Don’t Know If I Would Be Here: The Role of Families in Supporting Latinx Computer Science Students at HSIs
(2024-07-25) Rivera, Jessica; Núñez, Anne-Marie; Covarrubias, Igdalia
The underrepresentation of diverse communities in STEM disciplines, particularly in computer science, remains a significant challenge. This study investigates the experiences of Latinx students at Hispanic-Serving Institutions (HSIs) within computer science departments that are actively working to increase Latinx graduation rates. Utilizing data from ethnographic case studies, we conduct a thematic analysis through the lenses of Yosso’s community cultural wealth model and Rendón’s validation model to examine the pivotal role families play in fostering the success of Latinx students in computer science at HSIs. Our findings reveal that families provide essential encouragement, serve as a source of motivation to combat isolation, and celebrate students’ achievements in their pursuit of computer science careers. Recognizing the critical contributions of familial support is essential for enhancing the success of Latinx students in one of the most underrepresented fields within STEM. These insights are crucial for developing strategies that can effectively promote diversity and inclusion in computer science.
Metabolic Patterns of Fluconazole Resistant and Susceptible Candida auris Clade V and I
(2024-07-25) Barough, Robab Ebrahimi; Javidnia, Javad; Davoodi, Ali; Talebpour Amiri, Fereshteh; Moazeni, Maryam; Sarvi, Shahabeddin; Valadan, Reza; Siahposht-Khachaki, Ali; Moosazadeh, Mahmood; Nosratabadi, Mohsen; Haghani, Iman; Meis, Jacques F.; Abastabar, Mahdi; Badali, Hamid
Candida auris, an emerging non-albicans multidrug-resistant yeast, has become a significant cause of invasive candidiasis in healthcare settings. So far, data on the metabolites of C. auris in different clades are minimal, and no studies have focused on clade V metabolites. Therefore, Gas chromatography–mass spectrometry (GC-MS) was used for the metabolomic profiling of clade I C. auris compared with fluconazole-resistant and susceptible C. auris in clade V strains. GC-MS chromatography revealed 28, 22, and 30 compounds in methanolic extracts of the fluconazole-susceptible and fluconazole-resistant C. auris clade V and C. auris clade I strain, respectively. Some compounds, such as acetamide and metaraminol, were found in fluconazole-susceptible and resistant C. auris clade V and clade I. N-methyl-ethanamine and bis(2-ethylhexyl) phthalate metabolites were found in both fluconazole -susceptible and resistant C. auris clade V, as well as 3-methyl-4-isopropylphenol, 3,5-bis(1,1-dimethyl)-1,2-benzenediol, and diisostyl phthalate metabolites in both fluconazole resistant C. auris clade V and I. Identifying these metabolites contributes to understanding the morphogenesis and pathogenesis of C. auris, highlighting their potential role in antifungal drug resistance and the control of fungal growth. However, further experiments are warranted to fully comprehend the identified metabolites’ regulatory responses, and there may be potential challenges in translating these findings into clinical applications.
A Review of Research on Mathematics Teacher Educator Knowledge: Mapping the Terrain
(2024-07-25) Castro Superfine, Alison; Olanoff, Dana; Welder, Rachael M.; Prasad, Priya V.
Over the past two decades, the landscape of research on mathematics teacher educators (MTEs) has grown considerably. One particular area of interest has focused on MTE knowledge and the ways in which it is developed and used in teaching practice. However, studies have conceptualized MTE knowledge in different ways and have employed considerably different methodologies and approaches to its study. In an effort to understand this varied landscape, we conducted an extensive review of research on the nature and development of MTE knowledge. This review provides a broad descriptive analysis of the existing theoretical and empirical research on MTEs’ knowledge, explores the theoretical underpinnings of the existing frameworks for and studies on MTE knowledge, and considers implications for future research.
Synthesis of Cellulose-Based Hydrogel—Nanocomposites for Medical Applications
(2024-07-31) Al-Tarawneh, Wala`a; Hamadneh, Imad; Tarawneh, Ola; Al Najdawi, Ali
This study focused on synthesizing a cellulose-based hydrogel nanocomposite as a green hydrogel by adding a microcrystalline cellulose (MC) solution to carboxymethyl cellulose sodium (CMC-Na) with citric acid as a cross-linker. Y₂O₃ nanoparticles were incorporated during hydrogel preparation in different ratios (0.00% (0 mmol), 0.03% (0.017 mmol), 0.07% (0.04 mmol) and 0.10% (0.44 mmol)). FTIR analysis confirmed the cross-linking reaction, while XRD analysis revealed the hydrogels’ amorphous nature and identified sodium citrate crystals formed from the reaction between citric acid and CMC-Na. The swelling test in deionized water (pH 6.5) at 25 °C showed a maximum swelling percentage of 150% after 24 h in the highest nanoparticle ratio. The resulting cellulose hydrogels were flexible and exhibited significant antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The synthesized cellulose-based hydrogel nanocomposites are eco-friendly and suitable for medical applications.
Evolution Characteristics of Meteorological and Hydrological Drought in an Arid Oasis of Northwest China
(2024-07-24) Dan, Yier; Tian, Hao; Farid, Muhammad Arsalan; Yang, Guang; Li, Xiaolong; Li, Pengfei; Gao, Yongli; He, Xinlin; Li, Fadong; Liu, Bing; Li, Yi
In the context of global warming, the acceleration of the water cycle increases the risk of meteorological drought (MD) and hydrological drought (HD) in the arid region of Northwest China. The Manas River Basin is a typical agricultural oasis and the largest oasis farming area in Xinjiang, Northwest China. Droughts in this basin have significant implications for both agricultural production and the livelihoods of inhabitants. To evaluate the MD and HD and provide information for drought relief in the MRB, the standardized precipitation evapotranspiration index (SPEI) and standardized runoff index (SRI) were calculated using long-term rainfall and runoff data. Subsequently, combined with ArcGIS 10.3 software and the trend analysis method, the SPEI and SRI characteristics were evaluated at different time scales (1-, 3-, 6-, and 12-month). There were three main findings. First, both MD and HD were alleviated, with significantly more HD alleviation. MDs in spring and autumn exhibited a trend of aggravation. The SRIs in summer, autumn, and winter increased significantly at a confidence level of p < 0.01, with an insignificant decline in spring. In the 2010s, the frequency of light drought of MD was stable at 10% to 20%, while severe and extreme droughts increased. The frequency of HDs has decreased since the 1990s. Second, on annual and seasonal scales, MDs occurred mainly as light and moderate droughts. The highest frequency of MD was 24% of moderate droughts in winter. Spatially, the northern region of the MRB was characterized by more frequent light and extreme droughts. Third, runoff in the Manas River Basin increased significantly during the 1990s, which may have been related to the acceleration of glacial retreat in the Tianshan Mountains. This study can effectively reveal the changes in meteorological and hydrological drought in NWC and provide the basis for risk decision-making and management for watershed managers.
An Iterative Procurement Combinatorial Auction Mechanism for the Multi-Item, Multi-Sourcing Supplier-Selection and Order-Allocation Problem under a Flexible Bidding Language and Price-Sensitive Demand
(2024-07-17) Abbaas, Omar; Ventura, Jose A.
This study addresses the multi-item, multi-sourcing supplier-selection and order-allocation problem. We propose an iterative procurement combinatorial auction mechanism that aims to reveal the suppliers’ minimum acceptable selling prices and assign orders optimally. Suppliers use a flexible bidding language to submit procurement bids. The buyer solves a Mixed Integer Non-linear Programming (MINLP) model to determine the winning bids for the current auction iteration. We introduce a buyer’s profit-improvement factor that constrains the suppliers to reduce their selling prices in subsequent bids. Moreover, this factor enables the buyer to strike a balance between computational effort and optimality gap. We develop a separate MINLP model for updating the suppliers’ bids while satisfying the buyer’s profit-improvement constraint. If none of the suppliers can find a feasible solution, the buyer reduces the profit-improvement factor until a pre-determined threshold is reached. A randomly generated numerical example is used to illustrate the proposed mechanism. In this example, the buyer’s profit improved by as much as 118% compared to a single-round auction. The experimental results show that the proposed mechanism is most effective in competitive environments with several suppliers and comparable costs. These results reinforce the importance of fostering competition and diversification in a supply chain.
The Effects of Mental Fatigue on Anaerobic Power and Power Endurance Performance
(2024-07-16) Gonzalez, Matthew P.; Brown, Denver M. Y.; Swafford, Isabella M.; Summerville, Bryce; Seidi, Morteza; Hajiaghamemar, Marzieh; Dorgo, Sandor
Mental fatigue has been studied extensively in relation to its impact on aerobic-, strength-, and motor-based tasks, but anaerobic power-based tasks have received limited attention. Interdisciplinary research investigating the underlying mechanisms by which mental fatigue influences physical performance has been called for. In two studies, the effects of mental fatigue on maximal power jump and endurance jump performance as well as kinetics and kinematics during jump performance were examined. Samples of collegiate volleyball players (Study 1; N = 14) and recreationally active students (Study 2; N = 27) completed two 30 min experimental manipulations (high vs. low cognitive control exertion) before performing three maximal power squat jumps followed by 15 repeated countermovement jumps, with measurements of kinetics and kinematics. For Study 1, the maximal power performance was significantly lower under a mentally fatigued condition, but no differences were observed for repeated jump performance, which may have been attributable to alterations in jump mechanics. For Study 2, no between-condition differences were observed for the maximal power performance, although repeated jump performance was significantly lower under a mentally fatigued condition. Collectively, these findings suggest that the impacts of mental fatigue on power-based performance tasks may depend on the task demands as well as the training status of the individual.
Analysis of the Skin and Brain Transcriptome of Normally Pigmented and Pseudo-Albino Southern Flounder (Paralichthys lethostigma) Juveniles to Study the Molecular Mechanisms of Hypopigmentation and Its Implications for Species Survival in the Natural Environment
(2024-07-16) Blandon, Ivonne R.; DiBona, Elizabeth; Battenhouse, Anna; Vargas, Sean; Mace, Christopher; Seemann, Frauke
Southern flounder skin pigmentation is a critical phenotypic characteristic for this species’ survival in the natural environment. Normal pigmentation allows rapid changes of color for concealment to capture prey and UV light protection. In contrast, highly visible hypopigmented pseudo-albinos exhibit a compromised immune system and are vulnerable to predation, sensitive to UV exposure, and likely have poor survival in the wild. Skin and brain tissue samples from normally pigmented and hypopigmented individuals were analyzed with next-generation RNA sequencing. A total of 1,589,613 transcripts were used to identify 952,825 genes to assemble a de novo transcriptome, with 99.43% of genes mapped to the assembly. Differential gene expression and gene enrichment analysis of contrasting tissues and phenotypes revealed that pseudo-albino individuals appeared more susceptible to environmental stress, UV light exposure, hypoxia, and osmotic stress. The pseudo-albinos’ restricted immune response showed upregulated genes linked to cancer development, signaling and response, skin tissue formation, regeneration, and healing. The data indicate that a modified skin collagen structure likely affects melanocyte differentiation and distribution, generating the pseudo-albino phenotype. In addition, the comparison of the brain transcriptome revealed changes in myelination and melanocyte stem cell activity, which may indicate modified brain function, reduced melanocyte migration, and impaired vision.
Stakeholders’ Perceptions on the Implementation of the HPV Vaccine School-Entry Requirement in Puerto Rico during the COVID-19 Pandemic
(2024-07-10) Vázquez-Otero, Coralia; Medina-Laabes, Diana T.; Pérez-Guzmán, Derick; Díaz-Miranda, Olga L.; Mercado-Andino, Alondra K.; Escabí-Wojna, Erika I.; Colón-López, Vivian
This study explored the implementation of the human papillomavirus (HPV) vaccine school-entry requirement in Puerto Rico during the COVID-19 pandemic. We conducted 26 semi-structured interviews with stakeholders and community-based organizations from August 2021 to March 2022. The interview guide was developed using the 2009 Consolidated Framework for Implementation Research (CFIR). The interviews were recorded and transcribed in Spanish. Data were analyzed using applied thematic techniques. These themes included the following: (i) Intervention characteristics: Participants noted that the school-entry requirement was effective in increasing vaccination uptake prior to the pandemic. Issues with the immunization registry were noted; (ii) Outer setting: External influences, access barriers, and an increase in HPV vaccine exemptions since the implementation of the COVID-19 vaccine were discussed; (iii) Inner setting: Communication within organizations and HPV vaccination efforts improved as the pandemic progressed; (iv) Characteristics of individuals: Most agreed with the school-entry requirement, including exemptions; and (v) Process: Results showed the need to reinforce the population’s education about HPV and the vaccine. Implementation of the policy was challenging during the early stages of the pandemic due to measures enacted to stop the spread of COVID-19 and focus on the COVID-19 vaccine. Efforts to increase HPV vaccine should focus on increasing HPV vaccine education and creating collaborations.
Racial Micro-Affirmations: Latinx Close Friendships and Ethnic Identity Development
(2024-07-05) Mireles-Rios, Rebeca; Garcia, Nichole Margarita; Castro, Isaac M. J.; Hernandez, Monica; Cerda, Rodolfo
Through analysis of semi-structured interviews of 30 Latinx college students, we examined how Latinx students experience belonging, acceptance, and affirmations at a Hispanic-Serving Research Institution (HSRI) in California. Drawing from the theoretical perspectives of racial micro-affirmations, we uncovered two major themes: the importance of close friendships and the impact that ethnic studies courses have on ethnoracial identity development. This study contributes to the ongoing discussion of the on-campus experiences of underrepresented students as well as how to best serve and affirm them at HSRIs.
Differential Reinforcement without Extinction: An Assessment of Sensitivity to and Effects of Reinforcer Parameter Manipulations
(2024-06-28) MacNaul, Hannah; Cividini-Motta, Catia; Randall, Kayla
Although functional communication training (FCT) usually includes extinction, withholding reinforcement is not possible or ethical with certain individuals, for some topographies of problem behavior, or in certain contexts. The current study evaluates the effects of two variations of FCT, both without extinction, on problem behavior and communication. Further, the intervention procedures were designed to evaluate participant reactivity to reinforcer parameters (e.g., magnitude, delay, and quality) in the context of the FCT variations. The parameter sensitivity assessments were effective at identifying relevant reinforcer parameters for each participant and both FCT interventions were effective in decreasing problem behavior and increasing communication for all participants. The results demonstrated that FCT was effective regardless of which reinforcer parameter was manipulated. Moreover, all sessions were conducted in participants’ homes and caregivers reported high degrees of social validity for the intervention procedures and outcomes.
Tuning the Superspin Dynamics in Inverse Spinel Ferrite Nanoparticle Ensembles via Indirect Cation Substitution
(2024-06-22) Botez, Cristian E.; Price, Alex D.
We used magnetic and synchrotron X-ray diffraction measurements to investigate the possibility of tuning the strength of magnetic interparticle interactions in nanoparticle ensembles via chemical manipulation. Our main result comes from temperature-resolved in-phase ac-susceptibility data collected on 8 nm average-diameter Ni_0.25Zn_0.75Fe₂O₄ (Ni25) and Ni_0.5Zn_0.5Fe₂O₄ (Ni50) nanoparticles at different frequencies, χ′ vs. T|_f. We found that the relative peak temperature variation per frequency decade, ϕ=∆TT·∆log(f)—a known measure of interparticle interaction strength—exhibits a four-fold increase, from ϕ = 0.04 in Ni50 to ϕ = 0.16 in Ni25. This corresponds to a fundamental change in the nanoparticles’ superspin dynamics, as proven by the fit of phenomenological models to magnetic relaxation data. Indeed, the Ni25 ensemble exhibits superparamagnetic behavior, where the temperature dependence of the superspin relaxation time, τ, is described in the Dorman–Bessais–Fiorani (DBF) model: τT=τrexp⁡EB+EadkBT, with parameters τ_r = 4 × 10⁻¹² s, and (E_B + E_ad)/k_B = 1473 K. On the other hand, the nanoparticles in the Ni50 ensemble freeze collectively upon cooling in a spin-glass fashion according to a critical dynamics law: τ(T)=τ0TTg−1zν, with τ₀ = 4 × 10⁻⁸ s, T_g = 145 K, and zν = 7.2. Rietveld refinements against powder X-ray diffraction data reveal the structural details that underlie the observed magnetic behavior: an indirect cation replacement mechanism by which non-magnetic Zn ions are incorporated in the tetrahedral sites of the inverse spinel.

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