Equivalent Positions Research Articles

The In Vitro Functional Impairment of Thyroid Hormone Receptor Alpha 1 Isoform Mutants Is Mainly Dictated by Reduced Ligand Sensitivity.

Background: Thyroid hormone (TH) acts on TH receptors (TRs) and regulates gene transcription by binding of TRs to TH response elements (TREs) in target gene promoters. The transcriptional activity of TRs is modulated by interactions with TR-coregulatory proteins. Mutations in TRα cause resistance to thyroid hormone alpha (RTHα). In this study, we analyzed if, beyond reduced triiodothyronine (T3) affinity, altered interactions with cofactors or different TREs could account for the differential impaired transcriptional activity of different mutants. Methods: We evaluated four mutants derived from patients (D211G, M256T, A263S, and R384H) and three artificial mutants at equivalent positions in patients with RTHβ (T223A, L287V, and P398H). The in vitro transcriptional activity was evaluated on TRE-luciferase reporters (DR4, IR0, and ER6). The affinity for T3 and interaction with coregulatory proteins (nuclear receptor corepressor 1 [NCoR1] and steroid receptor coactivator 1 [SRC1]) were also determined. Results: We found that the affinity for T3 was significantly reduced for all mutants, except for TRα1-T223A. The reduction in the T3 sensitivity of the transcriptional activity on three TREs, the dissociation of the corepressor NCoR1, and the association of the coactivator SRC1 recruitment for each mutant correlated with the reduced affinity for T3. We did not observe mutation-specific alterations in interactions with cofactors or TREs. Conclusions: In summary, the degree of impaired transcriptional activity of mutants is mainly determined by their reduced affinity for T3.

HIV Capsid Inhibitors Beyond PF74.

Human immunodeficiency virus (HIV) capsid plays important roles at multiple stages of viral replication. At the initial stages, controlled uncoating (disassembly) of the capsid ensures efficient reverse transcription of the single-stranded RNA genome, into the double-stranded DNA. Whereas at later stages, a proper assembly of capsid ensures the formation of a mature infectious virus particle. Hence, the inhibition of capsid assembly and/or disassembly has been recognized as a potential therapeutic strategy, and several capsid inhibitors have been reported. Of these, PF-3450074 (PF74) has been extensively studied. Recently reported GS-CA inhibitors (GS-CA1 and GS-6207), have shown a strong potential and appear to contain a PF74 scaffold. The location of resistance mutations and the results of structural studies further suggest that GS-CA compounds and PF74 share the same binding pocket, which is located between capsid monomers. Additionally, phenylalanine derivatives containing the PF74 scaffold show slightly enhanced capsid inhibiting activity. A comparison of capsid structures in complex with host factors and PF74, reveals the presence of common chemical entities at topologically equivalent positions. Here we present the status of capsid inhibitors that contain PF74 scaffolds and propose that the PF74 scaffold may be used to develop strong and safe capsid inhibitors.

ACr(C2O4)2(H2O)4 (A = Li or Na): two new coordination polymers of low dimensionality with different hydrogen-bond networks.

Single crystals of two new bimetallic oxalate compounds with the formula [ACr(C2O4)2(H2O)4]n (A = Li or Na), namely catena-poly[[diaqualithium(I)]-μ-oxalato-κ4O1,O2:O1',O2'-[diaquachromium(III)]-μ-oxalato-κ4O1,O2:O1',O2'], (I), and catena-poly[[diaquasodium(I)]-μ-oxalato-κ4O1,O2:O1',O2'-[di-aquachromium(III)]-μ-oxalato-κ4O1,O2:O1',O2'], (II), have been synthesized, characterized and their crystal structures elucidated by X-ray diffraction analysis and compared. The compounds crystallize in the monoclinic space group C2/m for (I) and in the triclinic space group P-1 for (II); however, they have somewhat similar features. In the asymmetric unit of (I), the Li and Cr atoms both have space-group-imposed 2/m site symmetry, while only half of the oxalate ligand is present and two independent water molecules lie on the mirror plane. The water O atoms around the Li atom are disordered over two equivalent positions separated by 0.54 (4) Å. In the asymmetric unit of (II), the atoms of one C2O42- ligand and two independent water molecules are in general positions, and the Na and Cr atoms lie on an inversion centre. Taking into account the symmetry sites of both metallic elements, the unit cells may be described as pseudo-face-centred monoclinic for (I) and as pseudo-centred triclinic for (II). Both crystal structures are comprised of one-dimensional chains of alternating trans-Cr(CO)4(H2O)2 and trans-A(CO)4(H2O)2 units μ2-bridged by bis-chelating oxalate ligands. The resulting linear chains are parallel to the [101] direction for (I) and to the [11-1] direction for (II). Within the two coordination polymers, strong hydrogen bonds result in tetrameric R44(12) synthons which link the metal chains, thus leading to two-dimensaional supramolecular architectures. The two structures differ from each other with respect to the symmetry relations inside the ligand, the role of electrostatic forces in the crystal structure and the molecular interactions of the hydrogen-bonded networks. Moreover, they exhibit the same UV-Vis pattern typical of a CrIII centrosymmetric geometry, while the IR absorption shows some differences due to the oxalate-ligand conformation. Polymers (I) and (II) are also distinguished by a different behaviours during the decomposition process, the precursor (I) leading to the oxide LiCrO2, while the residues of (II) consist of a mixture of sodium carbonate and CrIII oxide.

Archaeological Excavation from Epistemological Perspective

Archaeological excavation as the basic form of fieldwork in archaeology is frequently perceived, especially in the Serbian archaeological community, as the focus of the archaeological method. The syllabi of university courses in methodology of archaeological research are often primarily devoted to the methods and techniques of excavation. The aim of this paper is to present a wider picture, i.e. to present the role of excavation in archaeological method from the point of view of epistemology as the general methodology of scientific research. Two questions are essential in this process: 1. What is the epistemological structure of archaeological research and what is the place of excavation? 2. Does archaeological excavation have any specific traits compared to structurally equivalent epistemological positions of other sciences, natural as well as social? Although it may seem that the answer to the first question is straightforward – excavation produces data for archaeological research – it is only partially true in reality, since the quantity and quality of data produced by excavation forms just a small part of the universe of data generated in archaeology in order to answer the research questions and to test hypotheses. Also, the majority of archaeological research is conducted on the already excavated material (and therefore independently of research questions and hypotheses of a later research project), and it is only rare that excavation is conducted as a research phase of a particular project, thus differing archaeology from the majority of other sciences, where the phase of gathering data (e.g. experiment or survey) follows the formulation of research objectives and hypotheses. This reflects the specific epistemological position of archaeological excavation, which is the consequence of the fact that archaeological excavation is not always linked to academic research, but is sometimes conducted in the absence of a definite research project (e.g. rescue excavations). At the same time, the destructive character of excavation raises the issue of replication of interpretation of stratigraphic relations and decisions on collecting and documenting the material. Archaeological excavation is the basic source of material on the grounds of which data are generated in the problem-oriented research, while the quantity of data generated by fieldwork excavation is limited to contextual-stratigraphic information. Non-replicability of archaeological excavation produces a strong need for detailed documentation during the process itself, but in order to be rational, the scope of this documentation is limited by the scope of existing methods. The paper presents possible models of growth of archaeological knowledge, favouring the model of declining benefits and relative finity of archaeological knowledge.

Unique Freezing Dynamics of Flexible Guest Cations in the First Molecular Postperovskite Ferroelectric: (C 5 H 13 NBr)[Mn(N(CN) 2 ) 3

Ferroelectricity is usually found in cubic and hexagonal perovskites consisting of corner- and faced-shared BX6 octahedra, respectively. In contrast, another important branch of perovskites, postpe...

Structural variations within proteins can be as large as variations observed across their homologues

Understanding the structural plasticity of proteins is key to understanding the intricacies of their functions and mechanistic basis. In the current study, we analyzed the available multiple crystal structures of the same protein for the structural differences. For this purpose we used an abstraction of protein structures referred as Protein Blocks (PBs) that was previously established. We also characterized the nature of the structural variations for a few proteins using molecular dynamics simulations. In both the cases, the structural variations were summarized in the form of substitution matrices of PBs. We show that certain conformational states are preferably replaced by other specific conformational states. Interestingly, these structural variations are highly similar to those previously observed across structures of homologous proteins (r2 = 0.923) or across the ensemble of conformations from NMR data (r2 = 0.919). Thus our study quantitatively shows that overall trends of structural changes in a given protein are nearly identical to the trends of structural differences that occur in the topologically equivalent positions in homologous proteins. Specific case studies are used to illustrate the nature of these structural variations.

The Conserved Tyr176/Leu177 Motif in the α-Helix 9 of the Feline Immunodeficiency Virus Capsid Protein Is Critical for Gag Particle Assembly

The capsid domain (CA) of the lentiviral Gag polyproteins has two distinct roles during virion morphogenesis. As a domain of Gag, it mediates the Gag–Gag interactions that drive immature particle assembly, whereas as a mature protein, it self-assembles into the conical core of the mature virion. Lentiviral CA proteins are composed of an N-terminal region with seven α-helices and a C-terminal domain (CA-CTD) formed by four α-helices. Structural studies performed in HIV-1 indicate that the CA-CTD helix 9 establishes homodimeric interactions that contribute to the formation of the hexameric Gag lattice in immature virions. Interestingly, the mature CA core also shows inter-hexameric associations involving helix 9 residues W184 and M185. The CA proteins of feline immunodeficiency virus (FIV) and equine infectious anemia virus (EIAV) exhibit, at equivalent positions in helix 9, the motifs Y176/L177 and L169/F170, respectively. In this paper, we investigated the relevance of the Y176/L177 motif for FIV assembly by introducing a series of amino acid substitutions into this sequence and studying their effect on in vivo and in vitro Gag assembly, CA oligomerization, mature virion production, and viral infectivity. Our results demonstrate that the Y176/L177 motif in FIV CA helix 9 is essential for Gag assembly and CA oligomerization. Notably, mutations converting the FIV CA Y176/L177 motif into the HIV-1 WM and EIAV FL sequences allow substantial particle production and viral replication in feline cells.

Structure, function and dynamics in acyl carrier proteins

Carrier proteins are four-helix bundles that covalently hold metabolites and secondary metabolites, such as fatty acids, polyketides and non-ribosomal peptides. These proteins mediate the production of many pharmaceutically important compounds including antibiotics and anticancer agents. Acyl carrier proteins (ACPs) can be found as part of a multi-domain polypeptide (Type I ACPs), or as part of a multiprotein complex (Type II). Here, the main focus is on ACP2 and ACP3, domains from the type I trans-AT polyketide synthase MmpA, which is a core component of the biosynthetic pathway of the antibiotic mupirocin. During molecular dynamics simulations of their apo, holo and acyl forms ACP2 and ACP3 both form a substrate-binding surface-groove. The substrates bound to this surface-groove have polar groups on their acyl chain exposed and forming hydrogen bonds with the solvent. Bulky hydrophobic residues in the GXDS motif common to all ACPs, and similar residues on helix III, appear to prohibit the formation of a deep tunnel in type I ACPs and type II ACPs from polyketide synthases. In contrast, the equivalent positions in ACPs from type II fatty acid synthases, which do form a deep solvent-excluded substrate-binding tunnel, have the small residue alanine. During simulation, ACP3 with mutations I61A L36A W44L forms a deep tunnel that can fully bury a saturated substrate in the core of the ACP, in contrast to the surface groove of the wild type ACP3. Similarly, in the ACP from E. coli fatty acid synthase, a type II ACP, mutations can change ligand binding from being inside a deep tunnel to being in a surface groove, thus demonstrating how changing a few residues can modify the possibilities for ligand binding.

Navigating within thiamine diphosphate-dependent decarboxylases: Sequences, structures, functional positions, and binding sites.

Thiamine diphosphate-dependent decarboxylases catalyze both cleavage and formation of CC bonds in various reactions, which have been assigned to different homologous sequence families. This work compares 53 ThDP-dependent decarboxylases with known crystal structures. Both sequence and structural information were analyzed synergistically and data were analyzed for global and local properties by means of statistical approaches (principle component analysis and principal coordinate analysis) enabling complexity reduction. The different results obtained both locally and globally, that is, individual positions compared with the overall protein sequence or structure, revealed challenges in the assignment of separated homologous families. The methods applied herein support the comparison of enzyme families and the identification of functionally relevant positions. The findings for the family of ThDP-dependent decarboxylases underline that global sequence identity alone is not sufficient to distinguish enzyme function. Instead, local sequence similarity, defined by comparisons of structurally equivalent positions, allows for a better navigation within several groups of homologous enzymes. The differentiation between homologous sequences is further enhanced by taking structural information into account, such as BioGPS analysis of the active site properties or pairwise structural superimpositions. The methods applied herein are expected to be transferrable to other enzyme families, to facilitate family assignments for homologous protein sequences.

The impacts of blanket on CFETR ohmic breakdown

China Fusion Engineering Test Reactor (CFETR) design is under way, it is necessary to develop an optimized scenario for plasma breakdown and current ramp-up, and to evaluate the consequent design constraints. A good initial magnetization (IM) and volt-seconds optimization are carried out for the ohmic breakdown based on the 2D TokSys model, giving the maximum volt-seconds that the magnetic coils can provide. Take IM as the initial condition, the ohmic breakdowns on the conditions that the blanket has different equivalent resistivities and positions are optimized. Comparisons of the optimized values and the target values are made. The ohmic breakdown without blanket is calculated as well, as a reference, the minimum equivalent resistivity of blanket required to meet the breakdown condition is obtained. Both initial magnetization and ohmic breakdown optimization could serve as preliminary references for the CFETR coils and blanket designs.

L amino acid transporter structure and molecular bases for the asymmetry of substrate interaction

L-amino acid transporters (LATs) play key roles in human physiology and are implicated in several human pathologies. LATs are asymmetric amino acid exchangers where the low apparent affinity cytoplasmic side controls the exchange of substrates with high apparent affinity on the extracellular side. Here, we report the crystal structures of an LAT, the bacterial alanine-serine-cysteine exchanger (BasC), in a non-occluded inward-facing conformation in both apo and substrate-bound states. We crystallized BasC in complex with a nanobody, which blocks the transporter from the intracellular side, thus unveiling the sidedness of the substrate interaction of BasC. Two conserved residues in human LATs, Tyr 236 and Lys 154, are located in equivalent positions to the Na1 and Na2 sites of sodium-dependent APC superfamily transporters. Functional studies and molecular dynamics (MD) calculations reveal that these residues are key for the asymmetric substrate interaction of BasC and in the homologous human transporter Asc-1.

A macroeconomic assessment of the impact of medical research expenditure: A case study of NIHR Biomedical Research Centres.

Quantifying the value of investment in medical research can inform decision-making on the prioritisation of research programmes. Existing methodologies to estimate the rate of return of medical research are inappropriate for early-phase translational research due to censoring of health benefits and time lags. A strategy to improve the process of translational research for patient benefit has been initiated as part of the UK National Institute for Health Research (NIHR) investment in Biomedical Research Centres (BRCs) in England. By providing a platform for partnership between universities, NHS trusts and industry, successful BRCs should reduce time lags within translational research whilst also providing an impetus for local economic growth through industry collaboration. We present a novel contribution in the assessment of early-phase biomedical research by estimating the impact of the Oxford Biomedical Research Centre (OxBRC) on income and job creation following the initial NIHR investment. We adopt a macroeconomic assessment approach using Input-Output Analysis to estimate the value of medical research in terms of income and job creation during the early pathway towards translational biomedical research. Inter-industry linkages are assessed by building a model economy for the South East England region to estimate the return on investment of the OxBRC. The results from the input-output model estimate that the return on investment in biomedical research within the OxBRC is 46%. Each £1 invested in the OxBRC generates an additional £0.46 through income and job creation alone. Multiplicative employment effects following a marginal investment in the OxBRC of £98m during the period 2007-2017 result in an estimated additional 196 full time equivalent positions being created within the local economy on top of direct employment within OxBRC. Results from input-output analyses can be used to inform the prioritisation of biomedical research programmes when compared against national minimum thresholds of investment.

Reproduction of a left-breast 3DCRT field-in-field radiation therapy planning in an anthropomorphic and anthropometric phantom

The proposal of this study was to reproduce the dosimetry established by a treatment planning system (TPS) following a 3D conformational radiation therapy (3DCRT) protocol of two parallel-opposite fields applied to the left-breast in a thorax phantom, with the complementary use of the field-in-field technique. The computed tomography (CT) images of the thorax phantom were transferred to the XiO version-5 for the elaboration of the breast teletherapeutic planning with 2 Gy per day, in 25 fractions, with prescribed dose of 50 Gy. A set of ten EBT2 radiochromic films were irradiated at doses gradually. The values of RGB (Red, Green, Blue) of the films were obtained by scanning and data transformed in optical density (OD), whose values were used to construct the calibration curve. Radiochromic films were positioned outside and inside of the thorax phantom. After phantom radiation at the linear accelerator 6 MV Elekta Precise were measured the intensities of the films in RGB by software ImageJ, transformed in OD and converted in bidimensional dose distributions, applying the calibration curve. In addition, graphics and dose-volume histograms (DVH) were developed. The dose measurements in the glandular-TE in breast did not present statistically significant differences in relation to values at equivalent positions generated in the TPS. The organs at risk received doses below the reference values, according to TPS. It was possible to reproduce the dosimetry prescribed in TPS into the thorax phantom exposed to a breast conformational teletherapy. The use of the radiochromic films in dosimetry proves to be increasingly useful and shall become routine in radiotherapy services.

Algorithm for the layout of a piezoelectric element in an elastic medium providing the maximal piezoelectric effect within a specified frequency range

ABSTRACTAn algorithm for the layout of a piezoelectric that provides the most efficient performance within a specified range of vibration frequencies is proposed in this paper. This algorithm is based on the consideration of a special parameter within the area of a piezoelectric element’s possible location. This parameter characterizes the superposition of electromechanical coupling coefficients’ for all the natural vibration frequencies included in a specified frequency range. The condition for defining the best option for location of the piezoelectric element in the case of several equivalent positions is specified. The efficiency of the proposed algorithm is shown numerically. The electromechanical coupling coefficients were calculated numerically based on solution to the problem of natural vibrations for electroelastic bodies using a finite element method. The calculations were performed to define the best location for a single piezoelectric element at the surface of a thin-walled shell having a half-cylindrical shape. The results are presented for natural vibration frequencies within the frequency range from 0 up to 1100 Hz. The numerical results were obtained by solving the problem of natural vibrations with a finite element method using the ANSYS software package.

Spin Polarization and Magnetic Properties of VGaON and VGaONInGa in GaN: GGA+U Approach

Electronic structure of a defect center containing the gallium vacancy and substitutional oxygen atom at nitrogen site (VGaON) in zinc blende and wurtzite GaN was analyzed within GGA+U approach. The +U term was applied to d(Ga), p(N), p(O), and d(In). Neutral VGaON is in the stable high spin state with spin S = 1. The defect structure is strongly dependent on geometry of the defect and the charge state. Two spin structures, which arise due to two different configurations in VGaON, with ON either along the c-axis or in one of three equivalent tetrahedral positions in wurtzite structure were analyzed. The weak ferromagnetic coupling between centers was found. The strength of magnetic coupling is increased when there is a complex containing VGaON with additional substitutional indium atom at the second neighbor to vacancy gallium site (VGaONInGa). Magnetic coupling between VGaONInGa is ferromagnetic due to strong spin polarization of p electrons of the nearest and distant nitrogen atoms.

The Canadian pediatric surgery workforce: A 5-year prospective study

BackgroundIn 2014, a survey study of the Canadian pediatric surgery workforce predicted a need for 2 new pediatric surgeons/yr. in Canada. We sought to assess these predictions and evaluate the status of the workforce. MethodsWith IRB approval, a web-based survey was sent to pediatric surgery division chiefs in Canada each year (2013–2017). The survey data included: number of practicing pediatric surgeons, full time equivalent (FTE) positions, and fellowship graduates. ResultsThere was a 100% response rate (18 divisions). From 2013 to 2017, the number of practicing pediatric surgeons and FTE positions increased (73 to 78, and 64.6 to 67.5, respectively). Eleven positions were vacated (4 retirement, 7 new practice), and 18 were filled. Eight were filled by new Canadian graduates, 7 by Canadians previously working in Canada or abroad, and 3 by European surgeons. Thirty-eight fellows completed training in Canada, including 24 non-Canadians who all left Canada. Nine Canadians who started practicing immediately after fellowship took positions in Canada (5) and the US (4). ConclusionsPredictions made in 2014 were largely accurate. There has been modest growth in the Canadian pediatric surgery workforce over the last 5 years. A significant mismatch continues to exist between Canadian pediatric surgery graduates and attending staff positions. Type of studySurvey. Level of evidenceV

Genotype-structure-phenotype relationships diverge in paralogs ATP1A1, ATP1A2, and ATP1A3.

ObjectiveWe tested the assumption that closely related genes should have similar pathogenic variants by analyzing >200 pathogenic variants in a gene family with high neurologic impact and high sequence identity, the Na,K-ATPases ATP1A1, ATP1A2, and ATP1A3.MethodsData sets of disease-associated variants were compared. Their equivalent positions in protein crystal structures were used for insights into pathogenicity and correlated with the phenotype and conservation of homology.ResultsRelatively few mutations affected the corresponding amino acids in 2 genes. In the membrane domain of ATP1A3 (primarily expressed in neurons), variants producing milder neurologic phenotypes had different structural positions than variants producing severe phenotypes. In ATP1A2 (primarily expressed in astrocytes), membrane domain variants characteristic of severe phenotypes in ATP1A3 were absent from patient data. The known variants in ATP1A1 fell into 2 distinct groups. Sequence conservation was an imperfect indicator: it varied among structural domains, and some variants with demonstrated pathogenicity were in low conservation sites.ConclusionsPathogenic variants varied between genes despite high sequence identity, and there is a genotype-structure-phenotype relationship in ATP1A3 that correlates with neurologic outcomes. The absence of “severe” pathogenic variants in ATP1A2 patients predicts that they will manifest either in a different tissue or by death in utero and that new ATP1A1 variants will produce additional phenotypes. It is important that some variants in poorly conserved amino acids are nonetheless pathogenic and could be incorrectly predicted to be benign.

The Impact of Strategic Fit on the Marketing Performance of the Industrial Corporations in Jordan

The present study aimed at identifying the impact of strategic fit on the marketing performance of the industrial corporations in Jordan. The population consists from all the Jordanian industrial corporations that are listed on Amman Stock Exchange. To be specific, the population consists from 63 companies. A sample was chosen through using the simple random sampling method. It was selected from 54 companies. Questionnaire forms were distributed to marketing, and administrative directors (or the ones holding equivalent positions).  76 questionnaire forms were retrieved (out of 108 questionnaires). All of the retrieved forms are valid for statistical analysis. The response rate is 70.37%. The latter rate is considered a good rate.
 
 Several results were concluded. For instance, it was found that the strategic fit has a statistically significant positive impact on the marketing performance of the Jordanian industrial corporations. The researchers recommend providing more attention to the achievement of strategic fit in the industrial corporations. That shall enable those companies to improve their marketing performance.

The human transketolase-like proteins TKTL1 and TKTL2 are bona fide transketolases

BackgroundThree transketolase genes have been identified in the human genome to date: transketolase (TKT), transketolase-like 1 (TKTL1) and transketolase-like 2 (TKTL2). Altered TKT functionality is strongly implicated in the development of diabetes and various cancers, thus offering possible therapeutic utility. It will be of great value to know whether TKTL1 and TKTL2 are, similarly, potential therapeutic targets. However, it remains unclear whether TKTL1 and TKTL2 are functional transketolases.ResultsHomology modelling of TKTL1 and TKTL2 using TKT as template, revealed that both TKTL1 and TKTL2 could assume a folded structure like TKT. TKTL1/2 presented a cleft of suitable dimensions between the homodimer surfaces that could accommodate the co-factor-substrate. An appropriate cavity and a hydrophobic nodule were also present in TKTL1/2, into which the diphosphate group fitted, and that was implicated in aminopyrimidine and thiazole ring binding in TKT, respectively. The presence of several identical residues at structurally equivalent positions in TKTL1/2 and TKT identified a network of interactions between the protein and co-factor-substrate, suggesting the functional fidelity of TKTL1/2 as transketolases.ConclusionsOur data support the hypothesis that TKTL1 and TKTL2 are functional transketolases and represent novel therapeutic targets for diabetes and cancer.

Order-disorder transition in the S = ½ kagome antiferromagnets claringbullite and barlowite.

The transition in the quantum magnets barlowite, Cu4(OH)6FBr, and claringbullite, Cu4(OH)6FCl is of an order-disorder type, where at ambient temperature interlayer Cu2+ ions are dynamically disordered over three equivalent positions. The disorder becomes static as the temperature is decreased, resulting in a lowering of symmetry. Ab initio density functional theory calculations explain this structural phase transition and provide insights regarding the differences between these two materials.