Domain Orientation Research Articles

In-line tempering eliminates the domain boundary in perovskite single crystals for high-energy resolution ionizing radiation detectors.

Metal halide perovskite single crystals (SCs) emerge as a promising candidate for ionizing radiation detection. The realization of top-performing radiation detectors typically relies on careful crystal selection from broad candidate groups, as residual strain remains unavoidable during the SC growth process, which often leads to the formation of ferroelastic domains with varied orientations. Here, we introduce an in-line tempering strategy to alleviate microstrain and homogenize the domain orientation across methylammonium lead iodide (MAPbI3) perovskite SCs. The progressive strain relief during the phase transition in situ, demonstrated by the removal of ferroelastic domain walls, substantially enhances the crystallinity and the optoelectronic properties of the MAPbI3 SCs. As a result, the gamma-ray energy spectrum detector leveraging these strain-relaxed SCs achieves an energy resolution of 7.2% at 59.5 keV for a 241Am gamma-ray source, and the 25-pixel device performs highly uniformly with concentrated current distribution, which paves the way for its implementation in high-resolution radiation spectroscopy.

Effect of sub‐coercive degradation on the local piezoelectric properties in lead zirconate titanate ceramics

AbstractLead zirconate titanate (PZT) is a widely recognized piezoelectric ceramic exhibiting excellent dielectric and ferroelectric properties over a wide range of temperature and frequency, making it desirable for applications such as capacitors, piezoelectric transducers, and actuators. Being subjected to repeated electrical loading in various applications, a progressive decrease in the functionality can happen, leading to device failure over time. Therefore, understanding degradation phenomena in all aspects is of importance to expand the lifespan of electronic devices. Despite of many studies focusing on the macroscopic properties of ferroelectrics related to degradation, such as switchable polarization, little is known about the change on local ferroelectric and piezoelectric properties and the domain structure induced by degradation. This paper reports the effect of sub‐coercive electrical cycling on local static and dynamic piezoelectric properties for PZT ceramic using piezoresponse force microscopy (PFM). The piezoelectric properties are probed along the three sample directions (x, y, z) to gain comprehensive insights into the local domain orientation throughout the bulk PZT sample which is then compared with microscopically measured piezoelectric coefficients. The PFM results are analyzed with respect to changes in domain orientation (depolarization) as well as to reduction on piezoelectric material response (degradation) to identify the origin of the degradation behavior. Our results directly show a strong depolarization effect in the direction of the applied electric field because of sub‐coercive cycling although it leads to small or even no degradation in directions perpendicular to the applied electric field. However, the latter is associated with a notable change in dynamic polarization switching properties which are strongly tied to the local domain structure. Our study shows that the origin of the degradation can be identified by analyzing the statistical change of local piezoelectric properties.

The Crystal Structure of Human IgD-Fc Reveals Unexpected Differences With Other Antibody Isotypes.

Of the five human antibody isotypes, the function of IgD is the least well-understood, although various studies point to a role for IgD in mucosal immunity. IgD is also the least well structurally characterized isotype. Until recently, when crystal structures were reported for the IgD Fab, the only structural information available was a model for intact IgD based on solution scattering data. We now report the crystal structure of human IgD-Fc solved at 3.0 Å resolution. Although similar in overall architecture to other human isotypes, IgD-Fc displays markedly different orientations of the Cδ3 domains in the Cδ3 domain dimer and the lowest interface area of all the human isotypes. The nature of the residues that form the dimer interface also differs from those conserved in the other isotypes. By contrast, the interface between the Cδ2 and Cδ3 domains in each chain is the largest among the human isotypes. This interface is characterized by two binding pockets, not seen in other isotypes, and points to a potential role for the Cδ2/Cδ3 interface in stabilizing the IgD-Fc homodimer. We investigated the thermal stability of IgD-Fc, alone and in the context of an intact IgD antibody, and found that IgD-Fc unfolds in a single transition. Human IgD-Fc clearly has unique structural features not seen in the other human isotypes, and comparison with other mammalian IgD sequences suggests that these unique features might be widely conserved.

Impact of the Lead‐Free Crystal Matrix 0.94NBaTiO3‐0.06SrTiO3 on the Photoluminescence Properties of Eu+3

The investigation reveals that the crystal field environment induces photoluminescence in Eu3+. These synthesized materials hold promise for a wide array of commercial applications, particularly in the light emitting diode industry, representing a significant advancement for the current generation of technology. The lead‐free electroceramics 0.94NB1−xEuxTiO3‐0.06SrTiO3 (x = 0 and x = 0.1) are fabricated using the conventional solid‐state reaction technique. Within these ceramics, both rhombohedral (R3c) and tetragonal (P4mm) structural phases coexist. The structural conformation and fluctuations in average grain size indicate the successful substitution of Eu3+ in 0.94NB1−xTiO3‐0.06SrTiO3 (x = 0). The incorporation of Eu3+ ions into the host matrix induces a long‐range ferroelectric state, marked by a rhombohedral (R3c) distortion, alongside enhanced tetragonal (P4mm) features. This structural modification results from the interaction between the Eu3+ ions and the host lattice, which fosters the emergence of a ferroelectric polarization. The coexistence of rhombohedral and tetragonal symmetries suggests a complex interplay of phases that collectively enhance the material's ferroelectric properties, potentially offering new avenues for applications in electronic and optical devices. Notably, compared to 0.94NB1−xEuxTiO3‐0.06SrTiO3 with (x = 0), the coercive field (Ec) significantly improves, while remanent polarization decreases in the presence of Eu3+. The domain orientation, particularly in Stage‐C, demonstrates a pronounced scaling behavior, which can be attributed to the crystal field surrounding the Eu3+ ions. This interaction influences the material's domain dynamics, enhancing its electromechanical properties. As a result, both of these lead‐free ceramics exhibit considerable potential for future electroceramic applications, offering a promising alternative in environmentally sustainable technologies.

Domain switching and shear-mode piezoelectric response induced by cross-poling in polycrystalline ferroelectrics

The mechanisms contributing to the electromechanical response of piezoelectric ceramics in the shear mode have been investigated using high-energy synchrotron x-ray diffraction. Soft lead zirconate titanate ceramic specimens were subjected to an electric field in the range 0.2–3.0 MV m−1, perpendicular to that of the initial poling direction, while XRD patterns were recorded in transmission. At low electric field levels, the axial strains remained close to zero, but a significant shear strain occurred due to the reversible shear-mode piezoelectric coefficient. Both the axial and shear strains increased substantially at higher field levels due to irreversible ferroelectric domain switching. Eventually, the shear strain decreased again as the average remanent polarization became oriented toward the electric field direction. The lattice strain and domain orientation distributions follow the form of the total strain tensor, enabling the domain switching processes to be monitored by the rotation of the principal strain axis. Reorientation of this axis toward the electric field direction occurred progressively above 0.6 MV m−1, while the angle of rotation increased from 0° to approximately 80° at the maximum field of 3.0 MV m−1. A strong correlation was established between the effective strains associated with different crystallographic directions, which was attributed to the effects of elastic coupling between grains in the polycrystal.

Characterizing the top trading cycles rule for housing markets with lexicographic preferences when externalities are limited

AbstractWe consider a housing market model with limited externalities where agents care both about their own consumption via demand preferences and about the agent who receives their endowment via supply preferences [we extend the associated lexicographic preference domains introduced in Klaus and Meo (Econ Theory 76:779– 811, 2023)]. If preferences are demand lexicographic, then our model extends the classical Shapley–Scarf housing market (Shapley and Scarf, J Math Econ 1:23–37, 1974) with strict preferences model. Our main result is a characterization of the corresponding top trading cycles (TTC) rule by individual rationality, pair efficiency, and strategy-proofness (Theorem 1), which extends that of Ekici (Theo Econ 19:551–564, 2024) from classical Shapley–Scarf housing markets with strict preferences to our model. Two further characterizations are immediately obtained by strengthening pair efficiency to either Pareto efficiency or pairwise stability (Corollaries 1 and 2). Finally, we show that as soon as we extend the preference domain to include demand lexicographic as well as supply lexicographic preferences (e.g., when preferences are separable), no rule satisfying individual rationality, pair efficiency, and strategy-proofness exists (Theorem 2).

Assessing Structures and Conformational Ensembles of Apo and Holo Protein States Using Randomized Alanine Sequence Scanning Combined with Shallow Subsampling in AlphaFold2 : Insights and Lessons from Predictions of Functional Allosteric Conformations.

Proteins often exist in multiple conformational states, influenced by the binding of ligands or substrates. The study of these states, particularly the apo (unbound) and holo (ligand-bound) forms, is crucial for understanding protein function, dynamics, and interactions. In the current study, we use AlphaFold2 that combines randomized alanine sequence masking with shallow multiple sequence alignment subsampling to expand the conformational diversity of the predicted structural ensembles and capture conformational changes between apo and holo protein forms. Using several well-established datasets of structurally diverse apo-holo protein pairs, the proposed approach enables robust predictions of apo and holo structures and conformational ensembles, while also displaying notably similar dynamics distributions. These observations are consistent with the view that the intrinsic dynamics of allosteric proteins is defined by the structural topology of the fold and favors conserved conformational motions driven by soft modes. Our findings support the notion that AlphaFold2 approaches can yield reasonable accuracy in predicting minor conformational adjustments between apo and holo states, especially for proteins with moderate localized changes upon ligand binding. However, for large, hinge-like domain movements, AlphaFold2 tends to predict the most stable domain orientation which is typically the apo form rather than the full range of functional conformations characteristic of the holo ensemble. These results indicate that robust modeling of functional protein states may require more accurate characterization of flexible regions in functional conformations and detection of high energy conformations. By incorporating a wider variety of protein structures in training datasets including both apo and holo forms, the model can learn to recognize and predict the structural changes that occur upon ligand binding.

Effects of thematic art programs on cognitive function and depressive symptoms in older adults

ABSTRACT The rapid aging of the global population underscores the need to employ innovative strategies, such as creative aging, to address the accompanying opportunities and challenges. This study investigated the effects of a thematic art program on cognitive abilities and depressive symptoms in older adults. An 8-week art program was developed. Participants attended weekly 2-hour sessions that focuses on connections with life experiences and the link between music and color. The study recruited 40 older adults aged between 60 and 90 years. Among the recruited older adults, 31 completed the entire program. The adults were recruited from community care centers in Northern Taiwan. The Montreal Cognitive Assessment, Stroop Color and Word Test, and Geriatric Depression Scale were used to assess cognitive and depressive symptoms. Participatory program observations and follow-up interviews were conducted to cross-check the results. Significantly improved cognitive abilities (in the overall cognitive function, visuospatial/executive, and orientation domains), executive function, and selective attention were observed. Additionally, the participants reported significantly reduced depressive symptoms. The intervention maintained and improved the physical and mental health of the participants. The empirical results provide a practical reference for developing art programs for older adults.

Cognitive patterns according to mini-mental state examination domains in patients with AF and association with all-cause mortality: a cluster analysis from a contemporary prospective study

Abstract Background Atrial fibrillation (AF) is associated with cognitive impairment even in the absence of previous stroke. However, data on specific patterns of cognitive impairment and their association with outcomes are limited. Purpose We aimed to identify different phenotypic groups of AF patients stratified according to specific cognitive domains using cluster analysis and evaluate the association between identified clusters and adverse outcomes. Methods We used data from a prospective observational study on AF patients excluding those with previous clinically overt stroke. We performed a hierarchical cluster analysis based on Ward’s Method using data from the Mini-Mental State Examination (MMSE) administered during the enrollment. The MMSE includes 6 distinct cognitive domains. We normalized each domain’s score from 0 to 100 to preserve the ranking and the interpretability of the test. Patients’ clusters were identified by examining the distance between cluster coefficients and by visual inspection of the dendrogram. All-cause mortality was the primary endpoint. Results A total of 872 stroke-free AF patients were included. Three clusters based on MMSE domains were identified: Cluster 1 (n=494, 56.7%); Cluster 2 (n=243, 27.9%) and Cluster 3 (n=135, 15.5%). The clusters greatly differed according to the cognitive domains affected and baseline characteristics (Table). The use of oral anticoagulants did not differ among clusters and it was substantially high (88.6%). Cluster 2 had a higher prevalence of cognitive impairment (37.9% vs 35.6% for Cluster 3 and 1.0% for Cluster 1, p<0.001) with a lower mean MMSE score compared to other clusters. The analysis of MMSE domains showed substantial deficits in the orientation, attention/calculation, and recall domains with peculiar differences among the clusters. Cluster 2 showed the most significant impairment in the copying domain (100%) while Cluster 3 had a higher impairment in attention/calculation and recall domains. After a median follow-up of 629 days, all-cause mortality was 15.9% with a significantly higher prevalence in Cluster 2 (26.9% vs 10.0% and 15.5% for Cluster 1 and Cluster 3 respectively, p<0.001). At the adjusted Cox regression analysis, Cluster 2 was independently associated with a higher risk of all-cause mortality compared with Cluster 1 (HR 1.83, 95% CI 1.18-2.82) while Cluster 3 was not independently associated with the outcome (Figure). Conclusions In a prospective observational cohort of stroke-free AF patients, we identified three clusters showing different patterns of cognitive impairment, affecting specific MMSE domains and resulting in a different risk of mortality. Our findings highlight the clinical implications of cognitive impairment and stress the need for a more holistic approach to AF patients including a comprehensive cognitive assessment, as well as the need for studies on interventions able to positively affect cognitive impairment.Figure

Understanding Iron-Doping Modulating Domain Orientation and Improving the Device Performance of Monolayer Molybdenum Disulfide.

Domain orientation modulation and controlled doping of two-dimensional (2D) transition-metal dichalcogenides (TMDCs) are two pivotal tasks for synthesizing wafer-scale single crystals and boosting device performances. However, realizing two such targets and uncovering internal physical mechanisms remain daunting challenges. We develop an accurate Fe doping strategy, which enables domain orientation control and electron mobility improvement of monolayer MoS2. By tuning of the Fe dopant dosages, parallel steps with different heights are formed, which induce edge-nucleation of unidirectionally aligned monolayer MoS2. In parallel, Fe doping induces the down shift of the conduction band minimum of monolayer MoS2 and matches well with the work function of an electrode, which reduces Schottky barrier height and delivers ultralow contact resistance (561 Ω μm) and excellent electron mobility (37.5 cm2 V-1 s-1). The modulation mechanism is clarified by combining theory calculations and electronic structure characterizations. This work hereby provides a new paradigm for synthesizing wafer-scale 2D TMDC single crystals and constructing high-performance devices.

Horizontal face information is the main gateway to the shape and surface cues to familiar face identity.

Humans preferentially rely on horizontal cues when recognizing face identity. The reasons for this preference are largely elusive. Past research has proposed the existence of two main sources of face identity information: shape and surface reflectance. The access to surface and shape is disrupted by picture-plane inversion while contrast negation selectively impedes access to surface cues. Our objective was to characterize the shape versus surface nature of the face information conveyed by the horizontal range. To do this, we tracked the effects of inversion and negation in the orientation domain. Participants performed an identity recognition task using orientation-filtered (0° to 150°, 30° steps) pictures of familiar male actors presented either in a natural upright position and contrast polarity, inverted, or negated. We modelled the inversion and negation effects across orientations with a Gaussian function using a Bayesian nonlinear mixed-effects modelling approach. The effects of inversion and negation showed strikingly similar orientation tuning profiles, both peaking in the horizontal range, with a comparable tuning strength. These results suggest that the horizontal preference of human face recognition is due to this range yielding a privileged access to shape and surface cues, i.e. the two main sources of face identity information.

In-plane and out-of-plane domain orientation dispersions in 1 to 3 monolayers epitaxial WS2 and MoS2 films on GaN(0001) film/sapphire(0001)

Transition-metal dichalcogenides and their heterostructures have attractive potential applications in electronics and optoelectronics. Wafer scale 1 to 3 monolayers WS2 and MoS2 ultrathin films on GaN/sapphire substrates were grown by metal organic chemical vapor deposition. Azimuthal reflection high-energy electron diffraction (ARHEED) was used to characterize the long-range order of these TMDC ultrathin films. The RHEED patterns of WS2 and MoS2 show stripes and arcs but the MoS2 on GaN shows sharp spots in addition to stripes and arcs. The 2D map constructed from ARHEED patterns shows that WS2 is epitaxial and has an in-plane domain orientation dispersion. For the MoS2 on GaN/sapphire substrate, the 2D map shows concentric continuous rings for each diffraction order of MoS2 and GaN indicating that the in-plane MoS2 domain orientation and GaN nanocrystals are random. The out-of-plane orientation dispersion of MoS2 on the GaN substrate is larger than that of WS2 on the GaN substrate. The observations of stripes, arcs, and spots from RHEED patterns and the 2D maps reveal the deviation of ultrathin epitaxial films from its perfect epitaxy, especially the TMDC domain orientation dispersion over a large area. These rich findings from 2D maps broaden the application of ARHEED in more than one monolayer thick 2D materials.

The impact of ePRO presentation during MDTB on clinician discussion of patient fitness and preferences: The INSPIRE intervention pilot.

251 Background: Treatment of pancreatic cancer often entails multiple modalities (e.g., chemotherapy, surgery, radiation) that vary in intensity, timing, and toxicity. While some options are only recommended for ‘fit’ patients regardless of age, formal fitness measures (such as the geriatric assessment [GA]) and patient preferences are seldom utilized during treatment decision-making. Methods: The INtegrating Systematic PatIent-Reported Evaluations into Multi-Disciplinary Tumor Board (INSPIRE-MDTB) intervention involves the presentation of GA and treatment preferences during MDTB discussions of patients with stage I-IV pancreatic adenocarcinoma. This qualitative study inductively analyzed, recorded and transcribed historical (November 2021 - February 2022) and intervention (September 2022 - June 2023) MDTBs using NVivo software. A constant comparative method was used to establish a grounded scheme representative of clinicians’ characterization of patients’ fitness and preferences during decision-making. Results: Recordings of the MDTB of 31 historical and 49 intervention patients with similar gender (52%; 53% female), age (m=68.1; 72.3), race (65%; 59% White), and cancer stage (26%; 22% stage IV) were included. The GA was not utilized in any historical case but was presented in 94% of intervention cases. Compared to historical controls, INSPIRE patients had more frequent discussions of (1) Cancer-Related Factors (e.g. size, location, progression speed; 35% vs. 43%), (2) Individual Risk Factors (e.g. age, comorbidities, tolerance; 90% vs 98%), and (3) Psychosocial Factors (e.g. health literacy, social support, substance use; 19% vs 33%) (Table 1). Preference domains were discussed in 39% of historical and 80% of intervention patients, with notable increases in patients’ concerns regarding physical (0%; 35%) and mental/emotional (0%; 20%) side effects, ability to work (0%; 10%), and the logistics and convenience of treatment (6%; 14%). Conclusions: INSPIRE-enhanced MDTB discussion of patient fitness and preferences represents a promising approach to providing a venue for consistent and systematic presentation and discussion of ePROs. Clinicians’ characterization of patients’ fitness during MDTB. Factors Impacting Fitness Baseline Intervention Cancer Related 11 (35%) 21 (43%) High Risk (size, location) 8 (26%) 16 (33%) Rapid Progression 0 (0%) 3 (6%) Prior or Concurrent Cancer 3 (10%) 3 (6%) Individual Risk Factor 28 (90%) 48 (98%) Age 19 (61%) 26 (53%) Comorbidities 24 (77%) 43 (88%) Weight Loss 11 (35%) 5 (10%) Tolerance 7 (23%) 9 (18%) Psychosocial Factor 6 (19%) 16 (33%) Insurance 2 (6%) 0 (0%) Language Barrier 0 (0%) 1 (2%) Health Literacy 0 (0%) 6 (12%) Social Support 3 (10%) 12 (24%) Substance use 1 (3%) 2 (4%)

Self-management behavior preferences and influencing factors in Chinese patients with recurrent gout: A qualitative study

ObjectiveThis study aimed to explore the preferences and influencing factors of self-management behaviors in patients with recurrent gout and provide a theoretical basis for developing targeted strategies to improve self-management preferences. MethodsA total of 10 patients with recurrent gout were recruited from the gout specialist outpatient clinic at a tertiary hospital in Shenyang, Liaoning Province, China. Semi-structured interviews were conducted with these patients, and the Kawakita Jiro (KJ) method was used to analyze the interview data. ResultsAfter four rounds of screening by five researchers, 35 codes were selected from an initial 132. After three rounds of discussion and induction, the KJ method identified seven domains of self-management behavior preferences in patients with recurrent gout: 1) extensive knowledge of gout, yet difficulty in distinguishing between accurate and inaccurate information; 2) a passive attitude of “no pain, no management”; 3) the challenge of changing entrenched daily habits; 4) the optimistic but unrealistic belief of “self-delusion”; 5) a tendency to seek medical attention late due to hopelessness of cure and familiarity with recurrences; 6) preference for analgesics for gout recurrences while neglecting long-term urate-lowering therapy (ULT); and 7) gout-related stigma. ConclusionThe results of this study showed that the self-management behavior of patients with recurrent gout could be improved, especially in the aspects of medical seeking behavior, medication compliance, daily management and emotional management. At the same time, we found that gout stigma, difficulty in distinguishing true and false knowledge of gout and negative attitude of “ignoring pain” were significantly associated with self-management behavior.

Effects of Ferroelastic Domain Walls on the Macroscopic Transport and Photoluminescent Properties of Bulk CsPbBr3 Single Crystals.

The all-inorganic halide perovskite CsPbBr3 has emerged as an excellent class of semiconductive and optoelectronic materials, in which its excellent properties are strongly related to the dynamics of its microstructures, i.e., ferroelastic domain walls. Here, the influence of ferroelastic domain walls on the macroscopic charge transport and photoluminescent properties in bulk single-crystal CsPbBr3 is experimentally and intrinsically studied across wide temperature intervals. The larger area of the same domain orientation, along with denser and thinner domain walls in a bulk CsPbBr3 single crystal, is formed through the Pnma↔P4/mbm↔Pm3̅m phase transitions. Remarkable motion of the domain walls near the P4/mbm↔Pm3̅m transition point is observed using in situ polarized optical microscopy. We initially observed a sharp decrease in resistivity after inducing larger areas with long-range order and denser, thinner domain walls in the temperature range from 273 to 343 K upon heating. In addition, the ferroelastic domain walls modulate exciton-phonon interactions and enhance radiative recombination in the CsPbBr3 single crystal, which correlates with the decrease in resistivity. These results will motivate strategies to design high-performance semiconductive and optoelectronic materials or devices by inducing specific ferroelastic domain walls in metal halide perovskites.

Ferromagnetism in High Entropy Cantor alloy triggered and tuned by severe plastic deformation

The process of severe plastic deformation (SPD) introduces unique conditions to materials, leading to the emergence of novel properties. This research specifically investigates the observation of deformation-induced ferromagnetism resulting from SPD processing. High-pressure torsion (HPT) is utilized to process both single-phase and nanocomposite high entropy alloys (HEAs). Vibrating sample magnetometry (VSM) confirms that HPT processing triggers the development of ferromagnetic properties. The distribution and alignment of magnetic domains post-SPD treatment are further examined using differential phase contrast scanning transmission electron microscopy (DPC STEM). Atom probe tomography (APT) analysis suggests that this phenomenon stems from the localized enrichment of ferromagnetic elements, particularly Ni, induced by deformation. This observation underscores the ‘cocktail effect’ in HEAs, whereby interactions between different elements has led to this unique magnetic behavior. Additionally, deliberate mechanical mixing of the CoCrFeMnNi alloy with a HfNbTaTiZr HEA, comprising non-ferromagnetic constituents, introduces a large rotational strain that alters the ferromagnetic properties. This mixing facilitates a transition from a random orientation of magnetic domains, as seen in the HPT-processed single CoCrFeMnNi alloy, to a coordinated alignment within the nanocomposite HEA.

Optimized magnetic properties of a Terfenol-D alloy in an extended temperature range using a high magnetic field

Tb–Dy–Fe alloys are among the most suitable magnetostrictive materials for high-power transducers. Optimizing magnetic properties in an extended temperature range could ensure the stable operation of transducers. In this work, a high magnetic field is applied to the directional solidification of Tb–Dy–Fe alloys. We study the microstructure, crystallographic orientation, magnetic susceptibility, crystal structure, and magnetic domain of samples. When the content and alignment of the magnetic phase along with crystallographic orientation remain basically invariant, the magnetic susceptibility of samples increases with the magnetic flux density of the high magnetic field throughout the temperature range from 273 K to Curie temperature (T C). At 4 T, the maximum magnetic susceptibility is increased by ∼ 40% compared with the sample without a high magnetic field applied, and the advantage is maintained in the range ∼ 300 K. Analysis shows that the enhancement of magnetic susceptibility is not due to the change in crystal structure, as commonly believed, but to the highly ordered alignment of magnetic domains. This research provides a new method for improving the temperature properties of magnetic materials using a high magnetic field.

Multiresolution molecular dynamics simulations reveal the interplay between conformational variability and functional interactions in membrane-bound cytochrome P450 2B4.

Cytochrome P450 2B4 (CYP 2B4) is one of the best-characterized CYPs and serves as a key model system for understanding the mechanisms of microsomal class II CYPs, which metabolize most known drugs. The highly flexible nature of CYP 2B4 is apparent from crystal structures that show the active site with either a wide open or a closed heme binding cavity. Here, we investigated the conformational ensemble of the full-length CYP 2B4 in a phospholipid bilayer, using multiresolution molecular dynamics (MD) simulations. Coarse-grained MD simulations revealed two predominant orientations of CYP 2B4's globular domain with respect to the bilayer. Their refinement by atomistic resolution MD showed adaptation of the enzyme's interaction with the lipid bilayer, leading to open configurations that facilitate ligand access to the heme binding cavity. CAVER analysis of enzyme tunnels, AquaDuct analysis of water routes, and Random Acceleration Molecular Dynamics simulations of ligand dissociation support the conformation-dependent passage of molecules between the active site and the protein surroundings. Furthermore, simulation of the re-entry of the inhibitor bifonazole into the open conformation of CYP 2B4 resulted in binding at a transient hydrophobic pocket within the active site cavity that may play a role in substrate binding or allosteric regulation. Together, these results show how the open conformation of CYP 2B4 facilitates the binding of substrates from and release of products to the membrane, whereas the closed conformation prolongs the residence time of substrates or inhibitors and selectively allows the passage of smaller reactants via the solvent and water channels.

Freeze-casting uniformity and domains

Freeze-casting is a technique for making centimeter long microchannel structures. Freeze-cast samples are often characterized from 2D cross-sectional images, resulting in weak determination of porosity and surface area as function of height of the sample. Here we analyze a freeze-cast 40 mm long sample of ▪ (LCSM) for which we have a full X-ray tomography dataset with a voxel size of 23.34×23.34×23.34μm3, as well as a high resolution cutout with a voxel size of 2.77×2.77×2.77μm3. We analyze the porosity and tortuosity and show that the latter is 1.17 and 1.27 for the solid and pore phase respective in the direction along the microchannels, but 5.12 and 8.83 in the perpendicular direction. We also quantify the domain structure of the freeze-casted pores and show that this is not uniform for the sample, but that the angular orientation and number of domains is preserved throughout the sample.

High depolarization temperature and low dielectric loss in high-temperature fine-grain composite piezoceramics

High depolarization temperature (Td) and low dielectric loss (tanδ) were obtained in Sc2O3/BiScO3-PbTiO3-Bi(Zn1/2Hf1/2)O3 (Sc2O3/BS-PT-BZH) high-temperature fine-grained composite piezoceramics prepared by high-energy ball milling and one-step pressureless sintering. The heterogeneous interfacial polarization effect and thermal stress between the Sc2O3 semiconductor secondary phase and the BS-PT-BZH perovskite piezoelectric matrix phase contribute to the polarization orientation of the ferroelectric domain in the electric field and the maintenance of the poled ferroelectric domain state under temperature excitation, respectively. Benefiting from the above two heterogeneous interfacial effects, the Sc2O3/BS-PT-BZH fine-grained (∼0.4 μm) ceramic exhibits a high Td of 349 °C, a low tanδ of 5.1 % and a moderate piezoelectric constant d33 of 495 pC/N, which are comparable to those of many BS-PT-based coarse-grained (>2 μm) ceramics. The advent of Sc2O3/BS-PT-BZH fine-grained piezoceramic is helpful to promote the development of high-performance miniaturized high-temperature piezoelectric devices.