Structural Analysis Research Articles

Enhanced Documentation and Evaluation of Grouting Process, through the Fusion of Non-Destructive Testing and Evaluation Information—The Case Study of the Katholikon of the Monastery of Panagia Varnakova

The restoration of historic buildings and structures involves a wide range of scientific and technical fields. The grouting process is among an array of rehabilitation and preservation interventions and aims to homogenize the structure after the implementation of strengthening measures. The process can provide important information regarding the state of preservation of the examined structure and correlate the progress of the process with the pathology of the monument. To achieve this, the analysis of typical raw grouting data is progressively fused with additional information from the diagnostic studies, non-destructive testing, geospatial information, and from the calculation and analysis of grouting indices. The restoration project of the Katholikon of the Monastery of Panagia Varnakova in Fokida, Greece was selected as the case study, due to its large scale and the severe earthquake damage it has sustained, which has necessitated comprehensive strengthening interventions and extensive grouting. The implementation of an integrated methodological approach validated the enhanced level of co-analysis, revealing information that is not readily deduced from a typical approach. Selected sub-areas of the Katholikon are presented, demonstrating how the observed pathology can be correlated with the results of the grouting process, while incorporating 3D data, and findings from structural and non-destructive analyses.

Insight into the microstructure and mechanical properties of Cu-20wt%Zn-xSn ternary alloy

The main objective of this research is to study the grain refinement and improved trend in mechanical properties of brass (Cu-20wt%Zn) doped with tin. Tin was added in concentrations of (x: 0.1, 0.3, 0.5, 0.8, and 1wt%). The alloy samples were produced by permanent die casting and machined to the required dimensions for the structural analysis and mechanical tests. Mechanical properties studied were percentage elongation, ultimate tensile strength, and Brinell hardness using a 100KN JPL tensile strength tester (Model: 130812) and portable dynamic hardness testing machine (Model: DHT-6) respectively. The structural analysis was conducted using an optical metallurgical microscope (Model: L2003A) and scanning electron microscopy (SEM) equipped with EDS. The results of the structural analysis showed that the control specimen consisted predominantly of coarse α-phase of zinc in copper (Cu3Zn). The samples doped with tin consisted of refined α-grains with patches of the second phase (Cu8Sn5). Mechanical test results indicated that the addition of tin to alpha brass improved the ultimate tensile strength and hardness with a slight decline in percentage elongation. The values recorded for ultimate tensile strength and Brinell hardness were 322MPa and 176HB respectively.

Redox‐Regulated Synthetic Channels: Enabling Reversible Ion Transport by Modulating the Ion‐Permeation Pathway

AbstractNatural redox‐regulated channel proteins often utilize disulfide bonds as redox sensors for adaptive regulation of channel conformations in response to diverse physiological environments. In this study, we developed novel synthetic ion channels capable of reversibly switching their ion‐transport capabilities by incorporating multiple disulfide bonds into artificial systems. X‐ray structural analysis and electrophysiological experiments demonstrated that these disulfide‐bridged molecules possess well‐defined tubular cavities and can be efficiently inserted into lipid bilayers to form artificial ion channels. More importantly, the disulfide bonds in these molecules serve as redox‐tunable switches to regulate the formation and disruption of ion‐permeation pathways, thereby achieving a transition in the transmembrane transport process between the ON and OFF states.

Material Optimization in Formula One Seat Fit Based on Structural and Biomechanical Analysis

F1 drivers have reported that they suffer a long-term lower back pain due to ‘Porpoising’ effect, it is a series of bounce that is generated due to Aerodynamic downforce. This downforce is part of drag reduction principle that pulls the air underneath the vehicle, thereby creating an incredible speed of 200 to 230 mph. Also at 200 mph speed, the driver experiences a high amount G-forces up to six times during the race. This can be simply avoided by increasing the ground clearance of vehicle but at the same time it also reduces the max speed of the vehicle. Hence, without compromising the speed, Design optimization is done for driver’s seat-fit through Computational methods of Biomechanical modelling and simulation for determining the optimum Seat Angle for Postural Ergonomics. As an additional Reinforcement and Shock absorption in seat material to protect driver’s spine from the resulting dynamics, Material optimization is done by selecting Graphene as the suitable material over the existing Carbon fiber material. Finite element method was carried out for structural analysis of seat-fit model. The stress, strain and deformation values were found to be lesser in Graphene model when compared to Carbon fiber. The simulation results will provide a solution for eliminating the higher risk of spine injury or pathological condition of a sportsman and thereby improves the sporting performance. Key Word: Motorsports, Computational Biomechanics, Ergonomics, Design optimization, Material optimization, Finite element analysis, Spine Injury prevention

The Effect of Financial Development, Tariff, and RTA on Exports: A Structural Gravity Analysis

This paper examines the effect of financial development (FD), tariffs, and RTA on bilateral exports in a structural gravity framework. Applying high-dimensional fixed effects in OLS and PPML estimation technique in a panel framework covering 169 countries over 2001-2017, this paper finds that FD of both exporters and importers are an important determinant for boosting exports. The EIA has the most trade creation effect than any other form of RTA. Importers' FD has a larger effect on bilateral exports for developed to developed and developed and developing country trade than that of the exporters. The trade between developing to developing countries is positively affected by both exporters' and importers' FD; and negatively to a larger extent by tariff measures. However, in the case of developing and developed country estimation, FD of the exporter country is significantly affecting bilateral trade. Tariffs significantly distort trade, largely between developing and developed countries.

Redox-Regulated Synthetic Channels: Enabling Reversible Ion Transport by Modulating the Ion-Permeation Pathway.

Natural redox-regulated channel proteins often utilize disulfide bonds as redox sensors for adaptive regulation of channel conformations in response to diverse physiological environments. In this study, we developed novel synthetic ion channels capable of reversibly switching their ion-transport capabilities by incorporating multiple disulfide bonds into artificial systems. X-ray structural analysis and electrophysiological experiments demonstrated that these disulfide-bridged molecules possess well-defined tubular cavities and can be efficiently inserted into lipid bilayers to form artificial ion channels. More importantly, the disulfide bonds in these molecules serve as redox-tunable switches to regulate the formation and disruption of ion-permeation pathways, thereby achieving a transition in the transmembrane transport process between the ON and OFF states.

A Novel Homoconjugated Propellane Triimide: Synthesis, Structural Analyses, and Gas Separation.

Rigid three-dimensional (3D) polycyclic propellanes have garnered interest due to their unique conformational spaces, which display great potential use in selectivity, separation and as models to study through-space electronic interactions. Herein we report the synthesis of a novel rigid propellane, trinaphtho[3.3.3]propellane triimide, which comprises three imide groups embedded on a trinaphtho[3.3.3]propellane. This propellane triimide exhibits large bathochromic shift, amplified molar absorptivity, enhanced fluorescence, and lower reduction potential when compared to the subunits. Computational and experimental studies reveal that the effective through-space π-orbitals interacting (homoconjugation) occurs between the subunits. Single-crystal XRD analysis reveals that the propellane triimide has a highly quasi-D3h symmetric skeleton and readily crystallizes into different superstructures by changing alkyl chains at the imide positions. In particular, the porous 3D superstructure with S-shaped channels is promising for taking up ethane (C2H6) with very good selectivity over ethylene (C2H4), which can purify C2H4 from C2H6/C2H4 in a single separation step. This work showcases a new class of rare 3D polycyclic propellane with intriguing electronic and supramolecular properties.

A plastic hinge method for static pushover analysis of 3D frame structures

ABSTRACT In this paper, a nonlinear elasto-plastic analysis method under incremental external loads is presented to determine static pushover curves of 3D frame structures. Geometric nonlinearity is taken into account with stability functions, and the nonlinear behaviour of material is considered by plastic hinge hypothesis. Improved matrices and matrix operations for 3D frame elements are given, and the results obtained from a six-storey 3D frame, which is used as a benchmark example, are given comparatively with the related studies. Furthermore, in order to perform these analyses with the developed algorithms, the upgraded computer program TUNAL is used to present pushover curves of a 2-storey RC building for an assumption on torsional stiffness caused by plastic hinges. It is shown that the proposed methodology and the computer program give accurate and reliable results.

Sharing and hiding knowledge under pandemics: The role of stressor appraisals, perceived supervisor behaviors and attributions of supervisor motives

AbstractThis study aims to shed light on the dual impact of appraisals of pandemic‐induced job stressors on employee knowledge sharing and hiding behaviors. Drawing on the transactional attribution model, we hypothesize that employee perceptions of supervisor compassionate and self‐serving behavior would positively mediate the impact of employee challenge and hindrance appraisals of pandemic‐induced job stressors on employee knowledge sharing and knowledge hiding, respectively. Moreover, stressor appraisals are expected to interact with employee attributions of supervisor compassionate and self‐serving motives in shaping perceptions of supervisor compassionate and self‐serving behavior, respectively. To test our hypotheses, we conducted two independent studies—a three‐wave full longitudinal study with 230 employees from UK and U.S. firms during the first COVID‐19 outbreak and a randomized scenario‐based experiment with 210 U.S. employees. Cross‐lagged structural equation analyses, analyses of variance, and path analyses fully supported our predictions, thus providing a nuanced understanding of the role of perceived supervisor behavior and attributions of supervisor motives in accounting for the differential effects of employee appraisals of pandemic‐induced job stressors on knowledge behaviors.

Effect of strontium fluoride on mechanical and remineralization properties of enamel: An in-vitro study on a modified orthodontic adhesive

ObjectivesEvaluate the ability of strontium fluoride on bond strength and enamel integrity after incorporation within orthodontic adhesive system as a delivery vehicle. MethodsExperimental orthodontic adhesive system Transbond™ XT were modified with 1% Sr2+, 0.5% SrF2, 1% strontium, 0.5% Sr2+, 1% F-, 0.5% F-, and no additions were control. Mixing of formulation was monitored using Fourier transform infrared spectroscopy. Small-molecule drug-discovery suite was used to gain insights into Sr2+, F-, and SrF2 binding. Shear bond testing was performed after 6-months of ageing. Enamel blocks were cut, and STEM pictures were recorded. Specimens were indented to evaluate elastic modulus. Raman microscope was used to collect Raman spectra and inspected using a scanning electron microscope. Crystal structural analysis was performed using X-ray diffraction. Effect of material on cellular proliferation was determined. Confocal was performed to evaluate the effect of formulation on biofilms. ResultsFTIR of modified adhesives depicted peak changes within range due to various functional groups existing within samples. TEM represented structurally optimized hexagonal unit-cell of hydroxyapatite. Mean shear bond strength is recorded highest for Transbond XT with 1% SrF2. Dead bacterial percentage appeared higher in 0.5% SrF2 and 1% F- specimens. Crystal lengths showed an increase in 0.5% and 1% SrF2 specimens. Phase contrast within TEM images showed a union of 0.5% SrF2 crystal with enamel crystal with higher elastic modulus and highly mineralized crystalline hydroxyapatite. Intensity of ν1 PO43- and ν1 CO32- along with carbonate - / ν1PO43- ratio displayed good association with strontium fluoride. The formulation showed acceptable cell biocompatibility (p < 0.353). All specimens displayed characteristic diffraction maxima of different apatite angles within XRD. SignificanceExperimental results suggested good biocompatibility, adequate mechanical strength, and far-ranging crystallization ability. This would provide a new strategy to overcome the two major challenges of fixed orthodontics, biofilm growth, and demineralization of enamel.

Enhancement of the rheological, dynamic mechanical, and morphological properties of thermoplastic natural rubber based on NR/PP blends using ENR/PP-g-MA as a compatibilizer

This study investigates the effects of incorporating a 50/50 blend of Epoxidized Natural Rubber/Polypropylene-grafted maleic anhydride (ENR/PP-g-MA) as a compatibilizing agent (CA) for a 70/30 Natural Rubber/Polypropylene (NR/PP) thermoplastic elastomer (TPE) on the technical properties such as structural analysis, rheological, dynamic mechanical and morphological properties. Formulations with varying CA concentrations (5 to 15 phr) were prepared using a Brabender plasticorder at 180°C for 10 min. The structural analysis was examined by Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (1H-NMR). The rheological behavior was examined using a Rubber Process Analyser (RPA). The dynamic mechanical properties were investigated by DMA. Atomic Force Microscopy (AFM) was used for the morphological examination. FTIR analysis confirmed reactions between the MA group in PP-g-MA and the epoxy groups in ENR, resulting in ENR-grafted PP with an ester and acid-based linkage. This reaction was evident during compatibilizer preparation. RPA results showed increased viscosity for both types of CAs compared to their individual values, confirming crosslinking reactions. Higher CA concentrations led to elevated viscosity and storage modulus. DMA results indicated that the compatibilization led to a significant enhancement in the storage modulus of the blends. Moreover, an increase in the glass transition temperatures (Tg) of the blends was produced. AFM examination revealed a more homogenous distribution of the dispersed PP phase for the CA-containing blends compared to the control NR/PP system.

Prevalence and Molecular Characterization of Vancomycin Variable Enterococcus faecium Isolated From Clinical Specimens.

Vancomycin variable Enterococcus (VVE) bacteria are phenotypically susceptible to vancomycin, but they harbor the vanA gene. We aimed to ascertain the prevalence of VVE among clinically isolated vancomycin-susceptible Enterococcus faecium (VSE) isolates, as well as elucidate the molecular characteristics of the vanA gene cluster within these isolates. Notably, we investigated the prevalence and structure of the vanA gene cluster of VVE. Between June 2021 and May 2022, we collected consecutive, non-duplicated vancomycin-susceptible Enterococcus faecium (VSE) samples. Real-time PCR was performed to detect the presence of vanA, vanB, and vanC. Overlapping PCR with sequencing and whole-genome sequencing were performed for structural analysis. Sequence types (STs) were determined by multilocus sequence typing. Exposure testing was performed to assess the ability of the isolates to acquire vancomycin resistance. Among 282 VSE isolates tested, 20 isolates (7.1%) were VVE. Among them, 17 isolates had partial deletions in the IS1216 or IS1542 sequences in vanS (N=10), vanR (N=5), or vanH (N=2). All VVE isolates belonged to the CC17 complex and comprised five STs, namely ST17 (40.0%), ST1421 (25.0%), ST80 (25.0%), ST787 (5.0%), and ST981 (5.0%). Most isolates were related to three hospital-associated clones (ST17, ST1421, and ST80). After vancomycin exposure, 18 of the 20 VVEs acquired vancomycin resistance. Considering the high reversion rate, detecting VVE by screening VSE for vanA is critical for appropriate treatment and infection control.

Semirational Design Based on Consensus Sequences to Balance the Enzyme Activity-Stability Trade-Off.

In this study, the phenomenon of the stability-activity trade-off, which is increasingly recognized in enzyme engineering, was explored. Typically, enhanced stability in enzymes correlates with diminished activity. Utilizing Rosa roxburghii copper-zinc superoxide dismutase (RrCuZnSOD) as a model, single-site mutations were introduced based on a semirational design derived from consensus sequences. The initial set of mutants was selected based on activity, followed by combinatorial mutation. This approach yielded two double-site mutants, D25/A115T (18,688 ± 206 U/mg) and A115T/S135P (18,095 ± 1556 U/mg), exhibiting superior enzymatic properties due to additive and synergistic effects. These mutants demonstrated increased half-lives (T1/2) at 80 °C by 1.2- and 1.6-fold, respectively, and their melting temperatures (Tm) rose by 3.4 and 2.5 °C, respectively, without any loss in activity relative to the wild type. Via an integration of structural analysis and molecular dynamics simulations, we elucidated the underlying mechanism facilitating the concurrent enhancement of both thermostability and enzymatic activity.

Simultaneous normal and reverse faulting in reactivating caldera faults: A detailed field structural analysis from Campi Flegrei (southern Italy)

Models of volcanic collapses proposed in the literature rely on combining field examples with analogue and numerical modelling to connect superficial observables to sub-surface volcano-tectonic processes. However, the behaviour of such collapses in an already faulted and fractured medium needs to be better explored.We studied a complex array of normal and reverse faults within the central sector of the active Campi Flegrei caldera, where faults with centimeters-to-meters displacements are hosted in the La Pietra tuff (∼13.5 ka) and the overlying pyroclastic succession of the last ∼5.5 kyr. We analyzed the attitude, kinematics and throw of these structures, employing a UAV-based digital outcrop model. The analysis shows that antithetic normal and reverse faults form in the hanging wall of a pre-existing WNW striking, NNE-dipping master normal fault. Moving northward, the strike of the antithetic faults rotates from WNW to NNW directions, with the latter showing a right-lateral oblique component. The simultaneity and coherence of both kinematics and attitudes are verified by the throw analysis. We associated the formation of this array with the caldera-collapse phase of the Agnano-Monte Spina eruption (∼4.55 ka), which caused off-caldera faulting beyond the main collapsed area.Based on field data, we suggest that during peak caldera-forming phases, wider areas beyond the main caldera scarps can be involved in volcano-tectonic collapses in the presence of a pre-existing fault network and complex tapped reservoirs. This highlights the role of inherited structures in weakening the crust above the magma reservoir that can potentially increase the magnitude and duration of caldera-forming eruptions, as they may induce a broader roof rock subsidence, pressurizing wider regions of the sub-caldera magma system.

Molecular mechanism of the one-component regulator RccR on bacterial metabolism and virulence.

The regulation of carbon metabolism and virulence is critical for the rapid adaptation of pathogenic bacteria to host conditions. In Pseudomonas aeruginosa, RccR is a transcriptional regulator of genes involved in primary carbon metabolism and is associated with bacterial resistance and virulence, although the exact mechanism is unclear. Our study demonstrates that PaRccR is a direct repressor of the transcriptional regulator genes mvaU and algU. Biochemical and structural analyses reveal that PaRccR can switch its DNA recognition mode through conformational changes triggered by KDPG binding or release. Mutagenesis and functional analysis underscore the significance of allosteric communication between the SIS domain and the DBD domain. Our findings suggest that, despite its overall structural similarity to other bacterial RpiR-type regulators, RccR displays a more complex regulatory element binding mode induced by ligands and a unique regulatory mechanism.

Computational Exploration of 1,2-Carboamine Carbonylation Catalyzed by Nickel.

Nickel-catalyzed carbonylation of alkenes is a stereoselective and regioselective method for the synthesis of amide compounds. Theoretical predictions with density functional theory calculations revealed the mechanism and origin of stereoselectivity and regioselectivity for the nickel-catalyzed carbonylation of norbornene. The carbonylation reaction proceeds through oxidative addition, migration insertion of alkenes, and subsequent reduction elimination to afford cis-carbonylation product. The C-N bond activation of amides is unfavorable because the oxidative addition ability of the C-C bond is stronger than that of the C-N bond. The determining step of stereoselectivity is the migratory insertion of the strained olefin. The structural analysis shows that steroselectivity is controlled by the steric hindrance of methyl groups to olefins and substituents to IMes in ligands.

Biocontrol Potential of Sodin 5, Type 1 Ribosome-Inactivating Protein from Salsola soda L. Seeds.

Sodin 5 is a type 1 ribosome-inactivating protein isolated from the seeds of Salsola soda L., an edible halophytic plant that is widespread in southern Europe, close to the coast. This plant, known as 'agretti', is under consideration as a new potential crop on saline soils. Considering a possible defence role of sodin 5 in the plant, we report here its antifungal activity against different halophilic and halotolerant fungi. Our results show that sodin 5 at a concentration of 40 µg/mL (1.4 µM) was able to inhibit the growth of the fungi Trimmatostromma salinum (35.3%), Candida parapsilosis (24.4%), Rhodotorula mucilaginosa (18.2%), Aspergillus flavus (12.2%), and Aureobasidium melanogenum (9.1%). The inhibition observed after 72 h was concentration-dependent. On the other hand, very slight growth inhibition was observed in the fungus Hortaea werneckii (4.2%), which commonly inhabits salterns. In addition, sodin 5 showed a cytotoxic effect on the Sf9 insect cell line, decreasing the survival of these cells to 63% at 1.0 µg/mL (34.5 nM). Structural analysis of sodin 5 revealed that its N-terminal amino acid residue is blocked. Using mass spectrometry, sodin 5 was identified as a homologous to type 1 polynucleotide:adenosine glycosylases, commonly known as ribosome-inactivating proteins from the Amaranthaceae family. Twenty-three percent of its primary structure was determined, including the catalytic site.

Metal Ions Can Modulate the Self-Assembly and Activity of Catalytic Peptide Amyloids.

Rational design of peptides has become a powerful tool to produce self-assembled nanostructures with the ability to catalyze different chemical reactions, paving the way to develop minimalistic enzyme-like nanomaterials. Catalytic amyloid-like assemblies have emerged among the most versatile and active, but they often require additional factors for activity. Elucidating how these factors influence the structure and activity is key for the design. Here, we showed that biologically relevant metal ions can guide and modulate the self-assembly of a small peptide into diverse amyloid architectures. The morphology and catalytic activity of the resulting fibrils were tuned by the specific metal ion decorating the surface, whereas X-ray structural analysis of the amyloids showed ion-dependent shape sizes. Molecular dynamics simulations showed that the metals can strongly affect the local conformational space, which can trigger major rearrangements of the fibrils. Our results demonstrate that the conformational landscape of catalytic amyloids is broad and tunable by external factors, which can be critical for future design strategies.

Solid-State Emissive Pillar[6]arene Derivative Having Alternate Methylene and Nitrogen Bridges.

Macrocyclic arenes show conformational adaptability, which allows host-guest complexations with the size-matched guest molecules. However, their emission properties are often poor in the solid states due to the self-absorption. Herein, we newly synthesized pillar[6]arene derivatives having alternate methylene and nitrogen bridging structures. Solvatochromic study reveals that the nitrogen-embedding into the cyclic structures can strengthen the intramolecular charge transfer (CT) nature compared to that of the linear nitrogen-bridged precursor. Owing to the large Stokes shift in the solid state, one of the nitrogen-embedded pillar[6]arenes shows high absolute photoluminescence quantum yield (ΦPL=0.36). Furthermore, it displays a turn-off sensing ability toward nitrobenzene (NB) vapor; a fluorescence quenching is observed when exposed to the NB vapor. From the structural analysis before and after the exposure of NB vapor, the amorphous nitrogen-embedded pillar[6]arene efficiently co-crystallize with NB and formed non-emissive intermolecular CT complexes with NB.

Record Second-Harmonic Generation and Birefringence in an Ultraviolet Antimonate by Bond Engineering.

Oxides have attracted considerable attention owing to their potential for nonlinear optical (NLO) applications. Although significant progress has been achieved in optimizing the structural characteristics of primitives (corresponding to the simplest constituent groups, namely, cations/anions/neutral molecules) comprising the crystalline oxides, the role of the primitives' interaction in determining the resultant functional structure and optical properties has long been underappreciated and remains unclear. In this study, we employ a π-conjugated organic primitive confinement strategy to manipulate the interactions between primitives in antimonates and thereby significantly enhance the optical nonlinearity. Chemical bonds and relatively weak H-bonding interactions promote the formation of cis- and trans-Sb(III)-based dimer configurations in (C5H5NO)(Sb2OF4) (4-HPYSOF) and (C5H7N2)(Sb2F7) (4-APSF), respectively, resulting in very different second-harmonic generation (SHG) efficiencies and birefringences. In particular, 4-HPYSOF displays an exceptionally strong SHG response (12 × KH2PO4 at 1064 nm) and a large birefringence (0.513 at 546 nm) for a Sb(III)-based NLO oxide as well as a UV cutoff edge. Structural analyses and theoretical studies indicate that polarized ionic bond interactions facilitate the favorable arrangement of both the inorganic and organic primitives, thereby significantly enhancing the optical nonlinearity in 4-HPYSOF. Our findings shed new light on the intricate correlations between the interactions of primitives, inorganic primitive configuration, and SHG properties, and, more broadly, our approach provides a new perspective in the development of advanced NLO materials through the interatomic bond engineering of oxides.