Additional Defects Research Articles

Quantifying defect production in solids at finite temperatures: Thermally-activated correlated defect recombination corrections to DPA (CRC-DPA)

It has long been recognized from low-temperature defect production experiments and molecular dynamics (MD) simulations of displacement events in metals that the surviving defect fraction relative to the calculated Norgett-Robinson Torrens (NRT) displacements per atom (dpa) ranges from ∼1 for near-threshold displacements (representative of electron irradiation) to ∼0.3 for energetic displacement cascades (relevant for fast neutrons or energetic heavy ion irradiations). This correlated point defect recombination that occurs within a few picoseconds following the creation of a primary knock-on atom (PKA) has recently been formalized in the athermal recombination corrected dpa (ARC-DPA) parameter. However, at elevated temperatures additional thermally-stimulated correlated defect recombination processes need to be considered. For example, at irradiation temperatures above defect recovery Stage I (typically ∼40–100 K for most metals), mobile self-interstitial atoms induce additional thermally-activated correlated defect recombination that can amount to 70–80% reduction in the surviving defect fraction for low PKA energies and ∼20 to 30% reduction for high PKA energies. Since most nuclear material applications involve operation above room temperature, it is generally important to include this additional correlated defect recombination in radiation effects models. Published experimental defect recovery and defect production studies on 26 metals are analyzed to extract the surviving defect fraction following thermally-activated correlated recombination as a function of PKA energy. These experimental estimates of the athermal- plus thermal-activated correlated recombination-corrected DPA (CRC-DPA) are compared with new long-term MD simulation results on Cu and Fe. The analysis indicates the CRC-DPA fraction of surviving defects in most elements for irradiation at temperatures where interstitials are mobile is ∼25% of the NRT DPA over a wide range of PKA energies relevant for electron, ion and fast neutron irradiation conditions. Limited experimental and kinetic Monte Carlo studies suggest a further reduction to ∼10% of the NRT DPA over a wide range of PKA energies when correlated recombination due to thermally activated vacancy migration is considered. This temperature-dependent CRC-DPA should be used as the defect production parameter (rather than NRT DPA or ARC-DPA) for materials irradiated at all temperatures where defects are mobile.

Current status and future promise of next-generation poly (ADP-Ribose) polymerase 1-selective inhibitor AZD5305.

The family of poly (ADP-ribose) polymerases (PARPs) consists of 17 members, which have been demonstrated as having effects on a series of cellular processes, including DNA replication and repair. PARP inhibitors (PARPi) suppress DNA repair through "PARP trapping", thus, constitute an important treatment option for cancer nowadays. In addition, PARP inhibition and homologous recombination repair (HRR) defects are synthetically lethal, giving a promising therapeutic for homologous recombination repair deficient (HRD) tumors including BRCA mutation. However, overlapping hematologic toxicity causes PARPi to fail in combination with some first-line chemotherapies. Furthermore, recent literature has demonstrated that PARP1 inhibition and PARP1-DNA trapping are key for antitumor activity in HRD cancer models. Currently approved PARPi have shown varying levels of selectivity for the entire 17-member PARP family, hence contribute to toxicity. Together, these findings above have provided the necessity and feasibility of developing next-generation PARPi with improved selectivity for PARP1, expanding significant clinical values and wide application prospects both in monotherapy and combination with other anticancer agents. In this review, we summery the latest research of current approved PARPi, discuss the current status and future promise of next-generation PARP1-selective inhibitor AZD5305, including its reported progress up to now and anticipated impact on clinical.

An additional simultaneous magnetic ordering and magneto-capacitive behavior with dielectric relaxation besides multiferroicity in FeTe x VO4

Here we report the evidence of an additional magnetic ordering and frequency dispersive magneto-dielectric (MD) permittivity besides multiferroic behavior in Te4+ (S = 0) doped FeVO4. Two antiferromagnetic transitions similar to FeVO4 at ∼21.86 K (T) and 16.03 K (T) were observed in all samples. An additional novel defect clusters based magnetic ordering at relatively higher temperature (T) ∼ 203 K is also observed from the magnetization. Evaluated magnetic moments show systematic decrease and the magnetic frustration factors show an increase with the increasing of Te4+ (S = 0) content. MD studies show stable ferroelectric ordering at spiral magnetic transition (T) and the multiferroic order persists to the largest doping of Te (x = 0.10). The MD studies also reveal a magneto-capacitive (MC) behavior at T (∼203 K) with a high dielectric constant and loss, and the possible reason for the magnetic ordering and MC behavior is ascribed to short range magnetic clustering arising out of defect based mechanisms. Mössbauer spectroscopic studies confirm local structural correlation with magnetic and ferroelectric ordering.

Thermoelectric enhancement for n-type PbS via synergistic effect of Ti doping and Cu2S compositing

PbS is identified as a potential alternative candidate material for thermoelectric power generation and refrigeration, owing to the resemblance with PbTe in crystal and band structures. However, the thermoelectric performance has reached a bottleneck because of its inferior electronic structure and high lattice thermal conductivity. This work focuses on optimizing the electron–phonon transport by the synergistic effect of Ti and Cu2S in n-type PbS. The first-principles calculation, single Kane band model, and Debye model reveal the physical origin of thermoelectric enhancement. The Ti doping introduces a donor-defect state, leading to a high electrical conductivity and a suppression of bipolar diffusion. However, the band structure of PbS is not ideally optimized due to the localization effect of the Ti resonant impurity states. Furthermore, the co-added Cu2S induces additional point defects, multiscale secondary phases, and Cu-rich precipitates at grain boundaries, which significantly scatter phonons in a wide frequency range and reduce the lattice thermal conductivity. As a result, the maximum zT of ∼0.8 at 823 K and the average zTave of ∼0.46 from 300 to 623 K are achieved in n-type Pb0.99Ti0.01S–2%Cu2S, demonstrating the important roles of Ti and Cu2S on improving thermoelectrics in n-type PbS.

Novel Approach to Improve the Identification of the Bleeding Phenotype in Noonan Syndrome and Related RASopathies

To characterize bleeding phenotype in Noonan Syndrome, to test the utility of following national guidelines in detecting this phenotype, to evaluate thromboelastography (TEG) as a diagnostic tool and to evaluate the cohort for genotype-phenotype correlations. Participants with a clinical diagnosis NS or related RASopathy were enrolled in a cohort study. Study procedures included clinical bleeding assessment, coagulation testing per guidelines and hematology consultation. TEG was completed in a subset and genetic testing was conducted for those without a molecular diagnosis. International Society of Haemostasis and Thrombosis Bleeding Assessment Tool (ISTH-BAT) scores were calculated with hematology consultation. Bleeding phenotype was defined as abnormal bleeding score. Twenty participants enrolled; 12completed clinical and laboratory evaluation, five of whom met the definition for bleeding phenotype. Four of the five participants with a bleeding phenotype had platelet aggregation defects and at least one additional coagulation defect. TEG was performed in nine participants, four with bleeding phenotype and five without, and results were normal in all cases. No genotype-phenotype correlation was found. Five of 20 participants had a bleeding phenotype identified. Based on available data we do not recommend incorporating TEG into clinical practice for NS patients. Platelet aggregation defects were the most common abnormalities, which would not be detected on Tier 1 testing of current guidelines, therefore we propose a new algorithm.

Fast electron contribution in electronic stopping for p-He and p-Ar collisions

Our study has shown that in collisions p-He and p-Ar with energies above 50 keV fast electrons carry away as kinetic energy up to 70 % of energy released during particle stopping. Ignoring the fast electron contribution makes impossible bringing independently measured cross sections of elementary processes of ionization, excitation, stripping and charge exchange into compliance with measured cross sections of electronic stopping. Fast electron emission in collisions of energetic ions with solids may induce extra radiation effects (create additional vacancies and defects in solid).Mean kinetic energies of ejected electrons We obtained from the analysis of cross section ratio agree well with directly measured energy spectra of the emitted electrons. The dynamic ionization theory implies the We proportionality to initial velocity v. In the considered cases, such a dependence takes place at the velocities below 2 a.u. At higher velocities, the observed dependence is successfully described in the framework of the Born approximation.

Mechanism of blistering of deformed coil coated sheets in marine climate

The tendency to blistering of coil coated steel sheets after deformation was investigated in both accelerated tests and marine climate. Corrosion processes played a crucial role in the blistering mechanism in deformed areas and blistering increased with induced strain. The inferior performance in deformed areas was associated mainly with higher permeability of organic coatings due to formation of additional defects. Localized water uptake measurements by the parallel plate capacitor technique were successfully applied to quantify the total damage to protective coatings induced by deformation. A link was found between blistering behaviour and the relative increase in water uptake.

Acute Vision Loss in Patients With Allergic Fungal Rhinosinusitis: A Case Series

Allergic fungal rhinosinusitis (AFRS) is a subtype of chronic noninvasive sinusitis accounting for 7.8% (0.2%-26.7%) of all chronic rhinosinusitis cases. A definitive diagnosis is usually made after sinus surgery. Successful treatment requires a combination of surgical and medical management. Although orbital involvement is relatively common, reports on optic neuropathy and acute vision loss are limited. Herein, we present a series of 3 patients with AFRS who presented with acute visual loss as the chief complaint. All 3 patients were otherwise healthy adults in their early 20s with extensive nasal polyps on endoscopic nasal examination and bone erosion in the bilateral orbits and lateral wall of the sphenoid sinus on the affected side on imaging. One of the 3 patients had bilateral cranial nerve IV defects in addition to cranial nerve III defects. All patients underwent endoscopic sinus surgery with orbital decompression and were followed up postoperatively by both otolaryngology and ophthalmology services with endoscopic and radiologic evaluation. Unfortunately, no meaningful improvement in vision was observed in any patient despite successful nerve decompression. Prompt diagnosis and early medical and surgical intervention are warranted to prevent complications in patients with AFRS with orbital extension.

Mid-Right Atrial Obstruction by an Aneurysmal Interatrial Septum Simulating an Additional Secundum Type Atrial Septal Defect.

Mid-Right Atrial Obstruction by an Aneurysmal Interatrial Septum Simulating an Additional Secundum Type Atrial Septal Defect.

A zeolite templating method for fabricating edge site-enriched N-doped carbon materials.

N-doped carbon materials have attracted considerable attention as highly functional materials because nitrogen doping distorts the carbon lattice, changes the charge density, and introduces additional defects. Among various positions of N atoms in N-doped carbon compounds, pyridinic-N, pyrrolic-N, and valley-N, which are doped at edge sites, exhibit specific electrocatalytic activities during the oxygen reduction reaction (ORR). However, it is difficult to selectively introduce these N atoms into a carbon matrix because the synthesis procedure typically includes high-temperature heat treatment. In this study, we applied a zeolite templating method to synthesize edge site-rich N-doped carbon materials. The sample fabricated using a zeolite template possessed high concentrations of pyridinic-N and valley-N atoms, demonstrating a significantly higher ORR catalytic activity than the sample synthesized without a zeolite template. Additional experiments conducted using various zeolites confirmed the positive effect of N-doped carbons on the ORR catalytic performance. This work demonstrated that the zeolite templating method not only increased the specific surface area and the number of active sites but also selectively created edge sites and improved the quality of the active sites.

A Prussian blue analog as a decorporation agent for the simultaneous removal of cesium and reactive oxygen species.

Radioactive cesium (Cs) is a significant concern due to its role as a major byproduct of nuclear fission and its potential for radioactive contamination. Internal contamination with radioactive Cs is characterized by immoderate production of reactive oxygen species (ROS), resulting in severe radiation damage. Therefore, the development of therapeutic strategies should focus on enhancing the excretion of radioactive Cs and reducing radiation-induced oxidative damage. However, current therapeutic drugs like Prussian blue (PB) have limited efficacy in addressing these issues. In this study, we present Cu3[Fe(CN)6]2 (CuFe) nanoparticles, a Prussian blue analog (PBA), which can not only efficiently sequester Cs but also exhibit resistance against radiation damage. The results of the adsorption studies demonstrate that CuFe outperforms PB in terms of adsorption performance. Further mechanistic investigations indicate that the increased adsorption capacity of CuFe may be attributed to the presence of additional defects resulting from the [Fe(CN)6] missing linkers. Moreover, CuFe mimics the functions of catalase (CAT) and superoxide dismutase (SOD) by effectively eliminating O2˙- and H2O2 while scavenging ˙OH, thereby mitigating ROS induced by radiative Cs. Importantly, in vivo study confirms the efficient Cs decorporation capability of CuFe. The fecal cumulative excretion rate of CuFe reaches 69.5%, which is 1.45 times higher than that of PB (48.8%). These findings demonstrate that CuFe exhibits excellent Cs removal performance and ROS scavenging ability, making it an attractive candidate for the treatment of Cs contamination.

Effect of gamma irradiation on the physical properties of MoS2 monolayer.

Two-dimensional transition metal dichalcogenides (2D-TMDs) have been proposed as novel optoelectronic materials for space applications due to their relatively light weight. MoS2 has been shown to have excellent semiconducting and photonic properties. Although the strong interaction of ionizing gamma radiation with bulk materials has been demonstrated, understanding its effect on atomically thin materials has scarcely been investigated. Here, we report the effect of gamma irradiation on the structural and electronic properties of a monolayer of MoS2. We perform Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) studies of MoS2, before and after gamma ray irradiation with varying doses and density functional theory (DFT) calculations. The Raman spectra and XPS results demonstrate that point defects dominate after the gamma irradiation of MoS2. DFT calculations elucidate the electronic properties of MoS2 before and after irradiation. Our work makes several contributions to the field of 2D materials research. First, our study of the electronic density of states and the electronic properties of a MoS2 monolayer irradiated by gamma rays sheds light on the properties of a MoS2 monolayer under gamma irradiation. Second, our study confirms that point defects are formed as a result of gamma irradiation. And third, our DFT calculations qualitatively suggest that the conductivity of the MoS2 monolayer may increase after gamma irradiation due to the creation of additional defect states.

NUMERICAL AND EXPERIMENTAL INVESTIGATION OF THE EFFECT OF DELAMINATION DEFECT AT MATERIALS OF POLYETHYLENE TEREPHTHALATE (PET)PRODUCED BY ADDITIVE MANUFACTURING ON FLEXURAL RESISTANCE

Polyethylene terephthalate (PET) material, which is widely used in the packaging industry due to its thermal and mechanical properties, high chemical resistance, and low gas permeability, is among the most widely used polymer materials in the world. These properties have made their use in additive manufacturing methods widespread. Determining how some common additive manufacturing defects affect the products produced by these methods will increase the adoption of these technologies in the final product production. In this study, the investigation of the effect of layer non-joining defect called delamination on the impact strength of PET material produced by additive manufacturing method at different layer thicknesses was carried out experimentally and numerically. The effects to flexural stress on the artificially created layer adhesion defect on the middle layers of the parts produced and modeled with a layer thickness of 0.1/0.2/0.3mm were investigated. It has been observed that the increase in layer thickness decreases flexural strength. In addition, while the flexural strength of the specimens containing delamination decreased, the increase in layer thickness accelerated this decrease.

Analysis of the dynamics of changes in gas content in oil-filled equipment with defects of various types

The article presents the results of analysing the dynamics of changes in the values of the ratios of characteristic gases, the percentage of gases, and defect nomograms in the process of developing electrical discharges, local overheating, and combined defects in high-voltage oil-filled equipment. During the analysis, the value of gas concentrations was evaluated for compliance with different levels regulated in the current Ukrainian standard at different stages of defect development. To determine the type of defect based on the values of the ratios of characteristic gases at different points in time, the norms regulated by the IEC 60599 standard and the ETRA square were used. The dynamics of changes in the percentage of gas was analysed using the Duval triangle. The results of the analysis showed that the primary defects during the development of electric discharges can be not only electric discharges with lower intensity, but also thermal (in particular, in the temperature range of 150-300 ℃) and combined defects. At the same time, in the process of discharge development, the nature of defects may change from measurement to measurement. Thus, when assessing the possibility of further operation of transformers, in addition to the degree of danger of the defect and the rate of its development, it is necessary to take into account the possibility of transforming the defect from a less to a more “dangerous” one that develops rapidly. During the development of thermal defects, the primary defect is usually a thermal defect with a lower hot spot temperature. It was found that in equipment with overheating above 700 ℃, the change in gas content during the development of the defect has a similar character. In particular, a mirror image of the change in the percentage of methane in relation to ethylene is observed. This effect can be used to detect high-temperature overheating at an early stage of its development, even before the gas concentrations exceed the limit values, which will help to avoid the destruction of equipment insulation and extend its service life. During the development of combined defects (overheating accompanied by discharges or discharges accompanied by heating), the main defect (e.g., discharge) first appears, and in the process of development, an additional defect (e.g., heating) develops. The results obtained indicate the possibility of detecting and recognizing defects in oil-filled equipment at different stages of their development.

Specific deletion of Axin1 leads to activation of β-catenin/BMP signaling resulting in fibular hemimelia phenotype in mice.

Axin1 is a key regulator of canonical Wnt signaling pathway. Roles of Axin1 in skeletal development and in disease occurrence have not been fully defined. Here, we report that Axin1 is essential for lower limb development. Specific deletion of Axin1 in limb mesenchymal cells leads to fibular hemimelia (FH)-like phenotype, associated with tarsal coalition. Further studies demonstrate that FH disease is associated with additional defects in Axin1 knockout (KO) mice, including decreased osteoclast formation and defects in angiogenesis. We then provide in vivo evidence showing that Axin1 controls limb development through both canonical β-catenin and BMP signaling pathways. We demonstrate that inhibition of β-catenin or BMP signaling could significantly reverse the FH phenotype in mice. Together, our findings reveal that integration of β-catenin and BMP signaling by Axin1 is required for lower limb development. Defect in Axin1 signaling could lead to the development of FH disease.

Performance Enhancement of Perovskite Quantum Dot Light-Emitting Diodes via Management of Hole Injection.

Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is widely used in optoelectronic devices due to its excellent hole current conductivity and suitable work function. However, imbalanced carrier injection in the PEDOT:PSS layer impedes obtaining high-performance perovskite light-emitting diodes (PeLEDs). In this work, a novel poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,40-(N-(p-butylphenyl))diphenylamine)] (TFB) is applied as the hole transport layers (HTLs) to facilitate the hole injection with cascade-like energy alignment between PEDOT:PSS and methylammonium lead tribromide (MAPbBr3) film. Our results indicate that the introduced TFB layer did not affect the surface morphology or lead to any additional surface defects of the perovskite film. Consequently, the optimal PeLEDs with TFB HTLs show a maximum current efficiency and external quantum efficiency (EQE) of 21.26 cd A-1 and 6.68%, respectively. Such EQE is 2.5 times higher than that of the control devices without TFB layers. This work provides a facile and robust route to optimize the device structure and improve the performance of PeLEDs.

Understanding the effect of low melting-point phases and homogenization annealing on the liquation cracks formation in the Al-Cu binary system during laser melting process

The alloy design is vital mission for eliminating the laser melting and additive manufacturing technologies defects. The low melting-point phases around the grain boundaries are considered as a source of the liquation cracks formation during laser melting process (LMP). In this work, a simple Al-Cu binary alloy with different Cu concentrations was selected as a model to understand the relation between low-melting point phases and liquation cracks formation during the LMP. In cast samples, most Al2Cu (θ phases) precipitate at the α-Al grain boundaries and during the LMP, the liquation cracks in the laser-melted zone (LMZ) initiated at the grain boundaries and propagated along the LMZ. Thus, homogenization annealing pre-laser melting at various times was done. The results showed that the cast Al-3.5Cu revealed high cracks susceptibility in the LMZ due to the presence of high amount of θ phases and during homogenization annealing the phases dissolved and the number of cracks significantly decreased. No cracks were formed in Al-7.5Cu at the cast and homogenized conditions due to the presence of many equilibrium eutectic θ phases, which heals the cracks (backfilling) during the solidification after the LMP. Liquation cracks susceptibility can be controlled by homogenization annealing.

Structural, Morphological, Electronic Structural, Optical, and Magnetic Properties of ZnO Nanostructures.

ZnO nanostructures were grown on a Si(111) substrate using a vapor-liquid-solid (VLS) growth procedure (pristine ZnO) and annealed via a rapid thermal-annealing process in an argon atmosphere at 1100 °C (Ar-ZnO). The synthesized ZnO nanostructures were investigated through structural, electronic structural, morphological, optical, and magnetic characterizations. X-ray diffraction and selective area electron diffraction (SAED) measurements revealed that both samples exhibited the hexagonal wurtzite phase of nanocrystalline ZnO. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy carried out at the O K-edge inferred the presence of the intrinsic-defect states. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy images displayed the formation of ZnO nanostructures. The photoluminescence (PL) spectra demonstrated an emission band in the UV region along with an additional defect band in the visible region. PL spectral analysis confirmed the presence of intrinsic defects in Ar-ZnO nanowires, contributing to the enhanced emission in the visible region. The Raman spectra showed the characteristic band (434 cm-1) corresponding to the vibrational modes of hexagonal wurtzite ZnO, with an additional band attributable to intrinsic defects. DC magnetization measurements showed a ferromagnetic response in both samples with enhanced coercivity in Ar-ZnO (~280 Oe). In brief, both samples exhibited the presence of intrinsic defects, which are found to be further enhanced in the case of Ar-ZnO. Therefore, it is suggested that intrinsic defects have played an important role in modifying the optical and magnetic properties of ZnO with enhanced results for Ar-ZnO.

Highly efficient visible light active doped metal oxide photocatalyst and SERS substrate for water treatment.

The development of efficient nanomaterials with promising optical and surface properties for multifunctional applications has always been a subject of novel research. In this work, the study of highly efficient TiO2 nanorods (NRs) and Ta-doped TiO2 NRs (Ta-TiO2 NRs) synthesized by alkaline hydrothermal treatment followed by soaking treatment has been reported. NRs were investigated for their potential applications as recyclable/reproducible visible light active photocatalysts and surface-enhanced Raman scattering (SERS) substrates in wastewater treatment. NRs were characterized by various microscopic (scanning and transmission electron microscopy), spectroscopic (X-ray diffraction, X-ray photoelectron, UV-visible, photoluminescence, and Raman spectroscopy), and surface (Brunauer-Emmett-Teller) techniques. The NRs exhibited promising optical properties with a band gap of 2.95eV (TiO2 NRs) and 2.58eV (Ta-TiO2 NRs) showing excellent photo-degradation activities for methylene blue (MB) dye molecules under natural sunlight. Particularly, Ta-TiO2 NRs showed enhanced response as visible light active photocatalysts in normal sunlight and also as SERS substrate attributed to the additional defects introduced by Ta doping. It could be explained by the combined effect of doping-induced enhanced visible light absorption and charge transfer (CT) properties of Ta-TiO2 NRs. Furthermore, Ta-TiO2 NRs were investigated for their long-term stability, reproducibility of the data, and recyclability in view of their potential applications in water treatment.

Amorphous structure and sulfur doping synergistically inducing defect-rich short carbon nanotubes as a superior anode material in lithium-ion batteries

Carbon anode materials have slow electron ion transport kinetics, which present challenges to the further practical application for lithium-ion batteries (LIBs). The morphology, crystallinity and defect structure of carbonaceous materials play crucial roles in the performance of LIBs. Herein, a defect-rich and sulfur-doped short amorphous carbon nanotubes (SACTs-S) with a hierarchical pore structure is reported and demonstrate their potential anode material in high-performance LIBs. Defect-rich structures are induced synergistically by sulfur doping and the amorphous nature of short amorphous carbon nanotubes. These defects not only endow the SACTs-S with additional active adsorption sites and good electrolyte/electrode interfacial compatibility but also improve diffusion kinetics of Li ions, thereby reducing Li ions migration barriers. These beneficial characteristics enabled the SACTs-S a high reversible capacity of 1608.7 mA h g−1 at 50 mA g−1 and an excellent cycle stability of 538.0 mA h g−1 over 2500 cycles at 2000 mA g−1. Also, the first-principle calculations reveal that additional defects created by sulfur doping can favor Li ions adsorption, conductivity enhancement and the reduction in Li ions diffusion barrier. This work thus presents an effective strategy for designing superior electrode materials for LIBs.