Greater Diffusion Research Articles

The Hypertextual Process of Rewriting a Plurimedial Work: Joan Fuster and Vicent Garcés’ Ballet Marinada

Joan Fuster is one of the most prolific and influential authors in Catalan culture. In 1953, the Valencian composer Vicent Garcés contacted Fuster to ask for his collaboration in writing a “Valencian opera”. Although this project will never come to fruition, it will lay the foundations of a friendship that will crystallise in Fuster’s only literary collaboration on a musical composition: the symphonic ballet Marinada, which was written in the late 1940s, during a stay of Garcés’ in Paris and premiered in València in 1957. The original lyrics, written by Garcés himself, were inspired by Valencian folk songs. Fuster’s intervention was decisive in providing the necessary literary quality that the work needed in order to win the 16th Joan Senent Ibañez award in 1972 and to have a greater diffusion. In this article, we intend, from a hypertextual perspective, to study the mechanisms that Fuster used in the process of rewriting Garcés’ text to turn a minor work into a composition recognised both musically and literarily. The correspondence between Garcés and Fuster and the analysis of the original scores and other work documents found in Fuster’s archive will allow us to describe the process of rewriting using an intermedial approach, as we will study a work that combines two media, i.e. music and literature.

Processing Parameter Setting Procedure for a Commercial Bowden Tube FDM Printer

Additive manufacturing (AM), especially fused deposition modeling (FDM), has experienced great development and diffusion during recent years. However, it still faces some limitations, such as poor dimensional accuracy or surface defects, the improvement of which motivates the elaboration of the present work. Contrary to an approach based on the optimization of parameters to obtain a single invariant value, the main objective of this study is the design of a procedure that anyone can follow to generate a printing profile for their specific FDM printer, environment, and imposed constraints through the adjustment of some selected parameters in the popular slicing software UltiMaker Cura. The resulting procedure consists of four ad hoc designed specimens and their analysis algorithms, all connected by a general workflow that ensures the correct execution of the procedure. Its applicability and effectiveness have been proved in a case study where a printing profile was developed for the real manufacturing project of a custom 3D object in polylactic acid (PLA), obtaining an improvement of 50% in tolerances and proving that the proposed parameter setting procedure represents a reduction in the setting time and material consumption versus conventional trial and error methodologies.

Multimodal gradients of basal forebrain connectivity across the neocortex

Cortical cholinergic projections originate from subregions of the basal forebrain (BF). To examine its organization in humans, we computed multimodal gradients of BF connectivity by combining 7 T diffusion and resting state functional MRI. Moving from anteromedial to posterolateral BF, we observe reduced tethering between structural and functional connectivity gradients, with the lowest tethering in the nucleus basalis of Meynert. In the neocortex, this gradient is expressed by progressively reduced tethering from unimodal sensory to transmodal cortex, with the lowest tethering in the midcingulo-insular network, and is also spatially correlated with the molecular concentration of VAChT, measured by [18F]fluoroethoxy-benzovesamicol (FEOBV) PET. In mice, viral tracing of BF cholinergic projections and [18F]FEOBV PET confirm a gradient of axonal arborization. Altogether, our findings reveal that BF cholinergic neurons vary in their branch complexity, with certain subpopulations exhibiting greater modularity and others greater diffusivity in the functional integration with their cortical targets.

Detection of Methane Leaks via a Drone-Based System for Sustainable Landfills and Oil and Gas Facilities: Effect of Different Variables on the Background-Noise Measurement

In recent years, thanks to the great diffusion of drone technology and the development of miniaturized sensors that can be connected to drones, in order to increase the sustainability of landfills and oil and gas facilities, interest in finding methane leaks and quantifying the relative flow has grown significantly. This operation requires the methane background concentration to be subtracted from the calculations. Therefore, in order to proceed with a right estimate of CH4 flows emitted, the possibility of correctly measuring or estimating the background level becomes crucial. The present work intends to illustrate the effects of different variables on the background-noise measurement in a drone-based system that uses a tunable diode laser absorption spectrometer (TDLAS). The methodology used is that of field testing; the data acquisition campaign consisted of the execution of 80 flights during which different flight variables (drone speed, flight altitude) were tested; the flights were repeated in different weather and climate conditions both during the same day and in different periods of the year. Different surfaces, similar to those found in landfill or natural gas sites, were also tested. In some of the field trials, a controlled methane release test was performed in order to verify how much the quantification of the methane flow can vary depending on the background level used. The results of the different field trials highlighted the best conditions under which to measure methane emissions with a TDLAS sensor in order to minimize the number of outliers: flight altitude not exceeding 15 m above ground level; the drone speed appears to have less impact on the results, however, it is optimal between 1 and 2 ms−1; a very sunny day produces much higher methane background levels than a cloudy one. The type of surface also significantly affects the measurement of background noise. Finally, tests conducted with a controlled methane release highlighted that different levels of background have a significant impact on the estimation of the methane flux emitted.

Incorporated surfaces and confined spaces of Na2HPO4·12H2O–Layered vermiculite nanosheets for phase change materials with enhanced thermal properties

The phase change process of hydrated salts with a large latent heat and non-flammable characteristics is a promising route for achieving energy-efficient devices. To improve the reliability of the inorganic phase change material (PCM) system, excellent heat storage capacity, low supercooling degree, and good stability of hydrated salts are required. In this study, novel Na2HPO4·12H2O (DHPD)–vermiculite nanosheet (VMTNS) composite PCMs (CPCMs) possessing both surfaces and confined spaces were theoretically designed and synthesized. Incorporating the environmentally friendly VMTNSs, a new type of nano-reinforced fillers with multiple active sites, into DHPD hydrated salt results in excellent crystallization, great diffusion ability (33.277 × 10−11 m2/s), a low supercooling degree (0.8 °C), a high latent heat of melting (260.7 J/g), and great thermal stability of CPCMs. The DHPD arrangement both in the confined spaces and on the surfaces of the VMTNSs was simulated via molecular dynamics calculations. It was found that the adsorption energy of DHPD in the confined spaces of the VMTNSs and on their surfaces is –5.991 and –5.543 eV, respectively. This study provides an innovative method to construct novel CPCMs for efficient energy storage.

Segmented Control of Selenization Environment for High-Quality Cu2ZnSn(S,Se)4 Films Toward Efficient Kesterite Solar Cells.

High-crystalline-quality absorbers with fewer defects are crucial for further improvement of open-circuit voltage (VOC) and efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. However, the preparation of high-quality CZTSSe absorbers remains challenging due to the uncontrollability of the selenization reaction and the complexity of the required selenization environment for film growth. Herein, a novel segmented control strategy for the selenization environment, specifically targeting the evaporation area of Se, to regulate the selenization reactions and improve the absorber quality is proposed. The large evaporation area of Se in the initial stage of the selenization provides a great evaporation and diffusion flux for Se, which facilitates rapid phase transition reactions and enables the attainment of a single-layer thin film. The reduced evaporation area of Se in the later stage creates a soft-selenization environment for grain growth, effectively suppressing the loss of Sn and promoting element homogenization. Consequently, the mitigation of Sn-related deep-level defects on the surface and in the bulk induced by element imbalance is simultaneously achieved. This leads to a significant improvement in nonradiative recombination suppression and carrier collection enhancement, thereby enhancing the VOC. As a result, the CZTSSe device delivers an impressive efficiency of 13.77% with a low VOC deficit.

Production of Green energy via Water Splitting mechanism by Mn- doped Cobalt Ferrites [Co1-xMnxFe2O4] based Hydroelectric Cells

In our current study, we have investigated the impact of manganese (Mn) doping on the structural, magnetic properties, and hydroelectric cell properties of cobalt ferrite with chemical formula [Co1-xMnxFe2O4, x=0.00, 0.125]. The solid-state approach has been utilized to synthesize the material. XRDmeasurements revealed the formation of an inverse spinel cubic structure with the space group Fd-3m. FTIR spectra hold a shift in the octahedral and tetrahedral bands with the increase in Mn content in cobalt ferrites. The subsequent rise in ferroelectric behavior has been observed with the net maximum saturation polarization of 1.08μC/cm2. The variation in the permittivity values has been also studied with the increase in Mn content for dry as well as wet hydroelectric cells. The impedance measurements helped us understand the contribution of grains/grain boundaries in the prepared ferrites. The enhanced value of magnetization has been noticed from 48.258 emu/g to 73.089 emu/g upon doping of Mn ions in cobalt ferrite spinel structure lattice.The Mndoped CFO exhibited enhanced performance in hydroelectric cells which demonstrates the great ionic diffusion mechanism with the incorporation of Mn ions. The obtained output makes Mn doped CFO a suitable material for studying microelectronic and hydroelectric cell applications. The purpose of this study is to enhance both ferroelectric as well as ferromagnetic behavior along with the improved value of current in hydroelectric cells.

Diffusion of tax-related communication on social media

Taxation is a recurrent topic in people's conversations, also on social media. Yet, informal channels such as social media have been widely neglected in studies that examined how information about taxation spreads across social networks. Using posts on Twitter (currently called “X”) with taxation related hashtags from 2010 to 2020, we examined what linguistic cues are associated with information diffusion, that is, the number of retweets a message receives. The use of emotional, moral, and moral-emotional language in a tweet was associated with greater diffusion (i.e., more retweets). In contrast to the negativity bias literature, positive emotional words were more strongly associated with information diffusion than negative emotional words. Among the specific emotions that taxation research has focused on, only the use of anger (but not anxiety) words was associated with more retweets. The study contributes to the literature by examining individuals’ reasoning about taxes.

Cortical microstructural associations with CSF amyloid and pTau

Diffusion MRI (dMRI) can be used to probe microstructural properties of brain tissue and holds great promise as a means to non-invasively map Alzheimer’s disease (AD) pathology. Few studies have evaluated multi-shell dMRI models such as neurite orientation dispersion and density imaging (NODDI) and mean apparent propagator (MAP)-MRI in cortical gray matter where many of the earliest histopathological changes occur in AD. Here, we investigated the relationship between CSF pTau181 and Aβ1–42 burden and regional cortical NODDI and MAP-MRI indices in 46 cognitively unimpaired individuals, 18 with mild cognitive impairment, and two with dementia (mean age: 71.8 ± 6.2 years) from the Alzheimer’s Disease Neuroimaging Initiative. We compared findings to more conventional cortical thickness measures. Lower CSF Aβ1–42 and higher pTau181 were associated with cortical dMRI measures reflecting less hindered or restricted diffusion and greater diffusivity. Cortical dMRI measures, but not cortical thickness measures, were more widely associated with Aβ1–42 than pTau181 and better distinguished Aβ+ from Aβ- participants than pTau+ from pTau- participants. dMRI associations mediated the relationship between CSF markers and delayed logical memory performance, commonly impaired in early AD. dMRI metrics sensitive to early AD pathogenesis and microstructural damage may be better measures of subtle neurodegeneration in comparison to standard cortical thickness and help to elucidate mechanisms underlying cognitive decline.

Enhanced transdermal delivery of apremilast loaded ethosomes: Optimization, characterization and in vivo evaluation

The low aqueous solubility and permeability of apremilast restricted its clinical efficiency in oral therapy for psoriasis arthritis. This research aimed to develop nanosized lipid carrier with high payload and can provide greater transdermal flux in an attempt to enhance the clinical efficiency of apremilast. Apremilast loaded ethosomes were efficiently formulated by a single-step injection technique. A 33 statistical Box-Behnken experimental design was employed to identify the optimum desirability of ethosomes by assessing the effect of three formulation components (soy lecithin, ethanol and apremilast) on responses such as vesicle size, drug entrapment and transdermal flux. The optimized ethosomes were formulated into a gel and evaluated for in vitro and in vivo characteristics including drug release, permeation and pharmacokinetics in rats. The optimization results indicated a significant effect (p < 0.05) of all three formulation variables on the responses evaluated. Optimized ethosomes exhibited spherical shape, nano-size with good payload and greater transdermal flux. The developed ethosomal gel had good physicochemical and rheological properties suitable for topical application and exhibited prolonged drug release by Weibull diffusion. A short lag time and higher transdermal flux (∼4 folds higher than control, p < 0.0001) noticed with ethosomes indicates rapid and greater diffusion through the skin barriers. Pharmacokinetic results demonstrated the potential of ethosomes in the transdermal therapy of apremilast as evidenced by the extent of absorption (AUC0-24, p < 0.0001) when compared with the oral counterpart. In nutshell, the data presented here establish the practical feasibility of ethosomal transdermal delivery and can be an alternative option for oral therapy in treating psoriasis arthritis.

Preferences of Young People in the Use of Facebook as a Health Education Tool for HPV

Abstract The accessibility and popularity of social networks makes them appropriate tools for promotion and prevention interventions in health, reaching a large audience with greater efficiency. One of its most attractive features is interaction, which not only allows great diffusion of the messages, but also supplies them with greater interest and credibility. Platforms such as Facebook are very popular among young people, a high risk group for Human papilloma virus (HPV) infection due to ignorance, prejudice and sexual behavior that is risked and active. The objective of this research is to know the preferences and attitudes of young people towards (1) interaction and (2) type of information about HPV on Facebook. Increasing our knowledge in this area will help to make interventions in this field more useful. Through a questionnaire validated in previous research, was made a cross-sectional descriptive study of the preferences of 120 young universities in the use of facebook as a tool for health promotion about HPV. More than half of the participants would follow a page on the HPV to be informed and share information on prevention, vaccines and campaigns. The preferred resources were: multimedia, testimonials and articles by specialists. They prefer to “share” to “create themselves” messages. A group of subjects who reject the use of the tool is detected, arguing that they would not do it for (1) a lack of interest, (2) because people can relate them personally to the sickness or (3) for possible bugs and criticisms.

Recent Progress in Synthesis of Nanostructures through Ion Exchange Route and their Applications

AbstractThe inorganic colloidal nanocrystals (ICNCs) have received a great deal of interest because of their tunable electronic and optical properties with coarse and finely controlled compositions, morphologies and thus, hybrid nanostructures have a wide range of applications in supercapacitor, luminescent solar concentrators (LSCs) and photothermal therapy (PPT). The ion exchange (IEx) process includes great diffusion rates of parent nanoparticles (NPs) ions from their crystal structure and their complete dissociation in specific solvents. The bond dissociation energies (BDEs) of different transition metal atoms with specific p‐block elements have been reviewed to analyze their effect on the IEx process. The alloy and doped and inorganic perovskite ICNCs have been synthesized via different IEx methodologies, showing varied photoluminescence quantum yields (PLQYs), nano‐dimensional morphology, composition, reaction time and temperature, and their performance for a specific application have been tabulated. The perovskite nanocrystals (NCs) are responsible for fast IEx dynamics that drop to homogenization in their composition, leading to NCs emitting in a narrow spectral region acting as an intermediate between those of the model NPs. The nanoscale metal‐organic particles (NMOPs) have opened plausible opportunities for their application in nanomedicine having highly enriched functionalities, well‐designed shapes/sizes, adjustable compositions, and intrinsic biodegradability. The potential to develop well‐designed heterostructures and for the growth of large‐area monocrystalline CsPbBr3 thin films provide a strong base for fundamental investigations of the intrinsic properties of perovskite‐based devices. The Cs3Sb2I9 is an active emitter layer that directs us toward low‐dimensional lead‐free A3B2X9 perovskite optoelectronic materials.

Masonry Arch Bridges with Finite Compression Strength Subject to Horizontal Longitudinal Seismic Actions

The great diffusion of masonry arch bridges, sometimes of historical interest, requires the development of simple but effective methodologies for a preliminary but reliable evaluation of their static and seismic capacity. In this paper, the behaviour under longitudinal seismic actions is analysed by using the mechanism method. The masonry is supposed to have no tension strength but a rigid–perfect plastic behaviour with finite strength in compression. The arch is subject to permanent loads and to a horizontal acceleration acting in the longitudinal direction, which causes a horizontal inertial loading acting on the arch. Three hypotheses about the effects of the inertial actions of the backfill are considered, which correspond to three different real behaviours. A comprehensive numerical investigation is performed, which allows us to point out the influence of the geometrical and mechanical parameters on the seismic capacity of a masonry arch bridge. The results are given by means of diagrams that can be easily used for a preliminary seismic check of a masonry arch bridge.

The Effect of Message Repetition on Information Diffusion on Twitter: An Agent-Based Approach

<bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Background:</b> Twitter offers tools that facilitate the diffusion of information by which companies can engage consumers to share their messages. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Literature review:</b> Communication professionals are using platforms such as Twitter to disseminate information; however, the strategies that they should use to achieve high information diffusion are not clear. This article proposes message repetition as a strategy. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Research questions:</b> 1. What is the wear-out point of Twitter? 2. How many times should a company repeat a tweet written on its brand page to maximize the diffusion for seeds? 3. How many times should a company repeat a tweet written on its brand page to maximize the diffusion while minimizing the number of consumers reaching their wear-out point for seeds? 4. How many times should a company repeat a tweet written on its brand page to maximize the diffusion for nonseeds? 5. How many times should a company repeat a tweet written on its brand page to maximize the diffusion while minimizing the number of consumers reaching their wear-out point for both seeds and nonseeds? <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Research methodology:</b> An agent-based simulation model for information diffusion is proposed as an approach to measure the diffusion of a tweet that has been repeated. The model considers that consumers can reach their wear-out point when they read a tweet several times. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Results:</b> The results of the model indicate the number of times a company should send the same tweet to achieve high information diffusion before this action has negative effects on consumers. Brand followers are key to achieving high information diffusion; however, consumers begin to feel bothered by the tweet by the sixth repetition. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Conclusions:</b> To the best of our knowledge, this is the first study to examine tweet repetition as a strategy to achieve higher information diffusion on Twitter. In addition, it extends the information diffusion literature by controlling the wear-out effect. It contributes to both communication and computational science literature by analyzing a communication problem using an agent-based approach. Finally, this article contributes to the field of technical and professional communication by testing a strategy to reach great information diffusion, and by creating a tool that any company can use to anticipate the results of a communication campaign created in Twitter before launching it.

Soil CO2 in organic and no-till agroecosystems

Increased carbon dioxide (CO2) concentrations in soil profiles could increase carbon sequestration via improved residence times of soil organic carbon (SOC), greater nutrient availability and plant growth, and via other pathways, but the effect of agricultural management techniques on soil CO2 is poorly understood. We used nondispersive infrared (NDIR) CO2 sensors to measure gas-phase CO2 concentrations in 1.50 m soil profiles in paired no-till (NT) and organic (ORG) agricultural systems in the Palouse region of eastern Washington State, USA, to investigate the effect of management on soil CO2. CO2 concentrations were significantly greater in ORG than in NT. The CO2 efflux into the atmosphere estimated using Fick's first law was generally greater in ORG due to both greater diffusivity and stronger concentration gradients observed in ORG. Results demonstrate that organic agriculture may facilitate greater soil CO2 concentrations and production rates. Further research is needed to quantify and understand the role of increased CO2 in soil carbon cycling in agroecosystems.

Post-Medieval Wrecks in the Western Mediterranean and Pottery: The Mortella II Wreck (1527) and the Chronology of Montelupo Tin-Glazed Earthenware

This paper discusses and underlines the importance of investigations on post-medieval shipwrecks, particularly for wrecks where archival documentation is also available, in relation to gaining a better knowledge of tin-glazed tableware produced in Montelupo (Florence, Tuscany). The case of the Mortella II wrecks is interesting in this sense and also shows how an exact dating of the wreck can allow for a revision of the chronologies of the ceramic classes found on board. In the case of the majolica of Montelupo, the revision of the dating of these ceramics with great diffusion (Europe, Americas, Africa) has major repercussions on international archaeological research. This paper presents a preliminary study of the Montelupo tin-glazed tableware found in the 2021 excavation researches conducted on the Mortella II wreck. The interest in the pottery recovered is high, for several reasons: (A) The dating of the wreck to 1527, clarified thanks to the discovery of a written document related to the sinking of the two Genoese “twin” ships off Saint-Florent (Haute-Corse), which are conventionally defined as Mortella II and III. (B) The almost exclusive presence of Montelupo majolica, a ceramic class among the most important between the 16th and 17th centuries, with a very wide dispersal throughout in the Mediterranean and Europe, as well as internationally. (C) The variety of decorations of the majolica of Montelupo documented thus far in the wreck (at least nine) makes this first sample a reference site for the study of this ceramic class in the first quarter of the 16th century, especially for the precise date of closure for the context (1527).

Influence of pressure on the circumferential diffusion characteristics of fuel vapor and combustion performance in a pressurized burner

To discuss the circumferential diffusion characteristics of the fuel vapor and combustion performance, a 15 kW pressurized burner fueled by diesel is first proposed in this research. And then, combustion experiments and cool-state numerical simulations are conducted at different pressures (P) and thermal loads (Q). The ratio (F) of the aerodynamic to buoyancy forces and the circumferential diffusion uniformity (σ) of the fuel vapor are constructed through pollutant emissions, fuel vapor concentration distribution and velocity field. The results show that under a Q of 3.55 kW, the burner has a relatively low F, and the buoyancy force has a more obvious effect as P increases, further causing circumferential fuel vapor distribution uniformity to suffer. When the burner operates at a Q of 10.64 kW, the undesired circumferential diffusion uniformity of the fuel vapor is only found at 0.3 MPa. For a Q of 15.37 kW, the fuel vapor has a great circumferential diffusion uniformity in the forward end of the liner at each P. A proper F of 89–278 and σ of 0–3.6% are recommended for diesel vapor circumferential diffusion and pollutant emissions, in which the buoyancy force has a relatively lower effect than the aerodynamic force.

Saint King Oswald of Northumbria: Overlord or Imperator? A Very Peculiar Ancestor

In the documentation produced by the English monarchy during the tenth century the Latin title imperator surprisingly appears, but it is not the first time that this title has been associated with an insular king. In Adomnán of Iona's Vita sancti Columbae (c.700), St. Oswald king of Northumbria appears as totius Britanniae imperator. Oswald, one of seven kings—successively called bretwaldas in the Anglo-Saxon Chronicle—who would have enjoyed a certain overlordship above other kingdoms of the island, could be the missing link connecting the use of the title imperator in the eighth and in the tenth centuries. Nevertheless, a closer view on the Oswald figure points out how he was remembered and worshipped more as a saint-overlord than as an emperor. Indeed, we can distinguish two different types of representation of the Northumbrian king’s authority: the first one proposed by Adomnán (emperor of Britain) and the second proposed by Bede (saintoverlord). In this article I show how the Bedian model had a greater diffusion than the Adomnán model in England in the following centuries, thanks to the cult of Oswald as a saint. This suggests that there was no direct link between the use of imperator in Adomnán and that in the tenth-century charters; they were two different manifestations of “imperiality.”

Efficient sulfur host based on Sn doping to construct Fe2O3 nanospheres with high active interface structure for lithium-sulfur batteries

Lithium-sulfur batteries are hampered by the shuttle effect and sluggish conversion kinetics of polysulfide, and give rise to serious capacity decay and poor rate performance, which is an important reason for limiting to commercialization applications. Herein, Sn-doped Fe2O3 nanospheres with high active interface structure adhere to adequate and high-efficiency catalytic sites have been designed by a facile hydrothermal reaction. Theoretical calculations of density of states (DOS), visualized detection, symmetric cyclic voltammetry and Li2S nucleation experiment can elucidate adsorption effect and the mechanism of promoting polysulfide conversion. When Sn@Fe2O3 with Sn doping molar ratio to 1:3, it can advance growth of Li2Sn (93.47 mAh·g−1), reduce the reaction energy barrier, and enhance the conversion of polysulfides. Thus, as a sulfur composite cathode active material, it shows low electrochemical charge transfer resistance (56.14 Ω) and great lithium-ion diffusion coefficient (DLi+ = 1.4 × 10−11 cm2·s−1). Meanwhile, it has a great initial discharge capacity of 1057 mAh·g−1 at 0.5 C along with 85 % discharge capacity retention at 1 C after 130 cycles. Encouragingly, even with a sulfur loading up to 1.2 mg cm−2, the sulfur composite cathode still can harvest high lithium-ion transfer efficiency and cyclic stability.

APOE4 genotype associations with longitudinal change in hippocampal microstructure

AbstractBackgroundApolipoprotein E4 (APOE4) is a major risk factor for late‐onset Alzheimer’s disease (AD). Associations between APOE4 genotype and hippocampal atrophy have been reported, but few longitudinal studies have evaluated microstructural changes. There is evidence that risk conferred by APOE4 may be partially driven by factors such as cerebral iron burden, neuronal injury, and inflammation. Brain iron concentration and other microstructural properties may be detected in vivo using quantitative susceptibility mapping (QSM) and diffusion‐weighted MRI (dMRI). Here, we characterized the effects of APOE4 genotype on longitudinal changes in hippocampal QSM and dMRI microstructural measures in a population‐based sample of adults from the UK Biobank (UKB).Method598 UKB participants of European ancestry (baseline age: 48‐78 years) with baseline and ∼2 year follow‐up brain MRI data were analyzed (Figure 1A). Four dMRI measures were derived from diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI; Figure 1B). Median dMRI and QSM hippocampal measures were extracted and averaged across hemispheres. For comparison with microstructure, bilateral hippocampal volume was also estimated. Linear regressions were used to test associations between change in six hippocampal measures (FollowUp‐Baseline) and number of E4 alleles (e3e3/e3e4/e4e4) adjusting for the time‐interval between scans, baseline MRI measure, age, sex, age‐by‐sex, age2, age2‐by‐sex, education, and the first 4 genetic ancestry principal components. Age‐dependent effects were explored in post‐hoc analyses including a sensitivity analysis stratifying associations by age (&lt; 65 or ≥ 65 yrs) and evaluation of APOE4‐by‐age interactions.ResultCompared to e3e3 homozygotes, E4 carriers had significantly greater increases in MD and ISOVF and greater decreases in ND (p&lt;critical FDR threshold; q=0.05; Table 1). E4 carriers ≥65 had nominally greater increases in MD and ISOVF and greater decrease in volume (p&lt;0.05); APOE4‐by‐age interactions were found for changes in ISOVF and volume (p&lt;0.05; Figure 2).ConclusionDisease risk conferred by the APOE4 genotype may be linked with greater inflammation (greater diffusivity) or neuronal loss. E4 associations with atrophy were only found in the subset of older participants, suggesting that detection of microstructural changes may precede volumetric changes in the hippocampus.