Negative Defects Research Articles

Hoxc10-mediated 'positional memory' regulates cartilage formation subsequent to femoral heterotopic grafting.

The Hox gene plays a crucial role in the bone development, determining their structure and morphology. Limb bone grafts expressing Hox positive genes are commonly used for free transplantation to repair Hox negative mandibular critical bone defects. However, the specific role of original Hox genes in newly formed bone during the cross-layer bone grafting healing process remains unexplored. Our findings demonstrate that femurs ectopically grafted into the mandibular environment retained a significant ability to differentiate into cartilage and form cartilaginous callus, which may be a key factor contributing to differences in bone graft healing. Hoxc10, an embryonic layer-specific genes, regulates cartilage formation during bone healing. Mechanistically, we observed Hoxc10 retention in co-cultured femoral BMSCs. Knocking out Hoxc10 narrows the bone gap and reduces cartilage formation. In summary, we reveal Hoxc10's 'positional memory' after adult cross-layer bone graft, influencing the outcomes of autologous bone graft.

Insight into insulation degradation mechanism of Al2O3 involved with positive and negative defects

Al2O3 with the desired electrical insulating properties and thermal shock resistivity has been extensively applied in the field of solid oxide fuel cells and oxygen sensors. However, degradation of the insulating Al2O3 layer is an intractable issue in practical applications. In this study, different point defect structures of Al2O3 were realized with the substitutional doping effect of ZrO2 and MgO. The MgO dopant provides positively charged oxygen vacancies, whereas the ZrO2 dopant tends to trigger negatively charged vacancy formation at Al3+ sites. The oxygen vacancy concentration of Al2O3 exhibits the following trend: MgO-doped Al2O3 > Al2O3 > ZrO2-doped Al2O3. Furthermore, the densification morphology, insulating properties, and oxygen vacancy migration of Al2O3 have been confirmed to be largely affected by the extrinsic factors. This study indicates that oxygen vacancy migration depends on the applied electric field at high temperatures. As the voltage and temperature increase, oxygen vacancy migration shows obvious electric-field-dependent characteristics, and its aggregation macroscopically shows hole defects. The defect position of Al2O3 is nonstoichiometric Al2O3-x with poor crystallinity. Therefore, it is believed that the oxygen vacancy migration triggered by the second phase directly determines the insulation performance and causes the degradation of Al2O3 materials.

In-situ polymerization of dual monomers for constructing a highly elastic PAA-co-PAM network enables efficient and stable Carbon-based perovskite solar cells

During the preparation of carbon-based perovskite solar cells, the external stress applied to the carbon paste inevitably compresses the perovskite lattice, potentially damaging its structure and generating defects. This poses a significant threat to the efficiency and stability of devices. Herein, a dual monomer irregular in-situ polymerization method was developed to form a highly elastic network (acrylamide-co-acrylic acid, PAA-co-PAM) within perovskite films, serving as both a ligament to passivate defects and a buffer to improve film stability under stress. The results demonstrated that multiple active sites of PAA-co-PAM could simultaneously passivate positive and negative defects, which improved charge transport efficiency, reduced nonradiative recombination, and prolonged lifetime of carriers. Meanwhile, the cross-linking network in PAA-co-PAM exhibits high elasticity due to both internal hydrogen bonds between monomers and external hydrogen bonds between monomers and perovskite, resulting in films with exceptional structural stability and mechanical resilience. Notably, the corresponding device achieved the power conversion efficiency of 15.39%. Moreover, the unencapsulated photovoltaic device passivated by the elastic network exhibits better storage stability and mechanical stability compared to the control devices. This work provides a new perspective and insight for comprehensively enhancing the stability of carbon-based perovskite solar cells.

F for Fantastic: Fostering Stability and Efficiency in Perovskite Solar Cells via Comb-Like Perfluoroalkyl-g-Polyethylenimine Additive.

Additive engineering has emerged as a promising strategy to address the inherent instability challenges of perovskite solar cells (PSCs) in the pursuit of commercial viability. However, achieving multifunctionality using a singular additive remains a considerable challenge. In this study, a novel comb-like multifunctional perfluoroalkyl-g-polyethylenimmonium iodide (FPEI·HI) as additives to the PbI2 precursor solution to facilitate the formation of high-quality and water-resistant perovskite films is presented. FPEI·HI establishes robust interactions with both formamidinium iodide (FAI) and PbI2, mediated by hydrogen bonding and Lewis acid-base interactions. These interactions play a pivotal role in simultaneously passivating negative and positive charged defects within the perovskite structure. Furthermore, the inclusion of perfluoroalkyl chains serves as resilience against moisture intrusion. As a consequence of these effects, a notably high device efficiency of 24.29% is achieved, demonstrating comprehensive improvement in various photovoltaic parameters compared to the control device (22.51%). Notably, unencapsulated devices exhibit remarkable stability in high-humidity environments, retaining 90% of their initial efficiency even after 2500h of storage. This work underscores the efficacy of FPEI·HI as a critical enabler for enhancing the stability and efficiency of perovskite solar cells, marking a significant stride toward their commercialization.

In-grown and irradiation-induced Al and N vacancies in 100 keV H+ implanted AlN single crystals

We report positron annihilation results on in-grown and proton-irradiation-induced vacancy defects in AlN single crystals grown by physical vapor transport. The samples were irradiated with 100 keV H+ ions to varying fluences in the range of 5 × 1014 − 2 × 1018 ions cm–2. Doppler broadening of annihilation radiation was recorded in as-grown and irradiated samples with a slow positron beam with varying implantation energy. Doppler results combined with first principles theoretical calculations show that the 100 keV H+ irradiation introduces isolated VAl on the ion track and VN-rich vacancy clusters at the end of the ion range. The results suggest that the excess amount of detected VN originates from a high concentration of in-grown VN. So far, these defects have been considered to be unidentified negative ion-like defects in AlN.

Active nematic ratchet in asymmetric obstacle arrays.

We numerically investigate the effect of an asymmetric periodic obstacle array in a two-dimensional active nematic. We find that activity in conjunction with the asymmetry leads to a ratchet effect or unidirectional flow of the fluid along the asymmetry direction. The directional flow is still present even in the active turbulent phase when the gap between obstacles is sufficiently small. We demonstrate that the dynamics of the topological defects transition from flow mirroring to smectic-like as the gap between obstacles is made smaller, and explain this transition in terms of the pinning of negative winding number defects between obstacles. This also leads to a nonmonotonic ratchet effect magnitude as a function of obstacle size, so that there is an optimal obstacle size for ratcheting at fixed activity.

Non-targeted analysis of per- and polyfluorinated substances in consumer food packaging

This study sought to develop a non-targeted workflow using high-resolution mass spectrometry (HRMS) to investigate previously unknown PFAS in consumer food packaging samples. Samples composed of various materials for different food types were subjected to methanolic extraction, controlled migration with food simulants and total oxidizable precursor (TOP) assay. The developed HRMS workflow utilized many signatures unique to PFAS compounds: negative mass defect, diagnostic breakdown structures, as well as retention time prediction. Potential PFAS features were identified in all packaging studied, regardless of food and material types. Five tentatively identified compounds were confirmed with analytical standards: 6:2 fluorotelomer phosphate diester (6:2 diPAP) and one of its intermediate breakdown products 2H-perfluoro-2-octenoic acid (6:2 FTUCA), perfluoropentadecanoic acid (PFPeDA), perfluorohexadecanoic acid (PFHxDA) and perfluorooctadecanoic acid (PFOcDA). Longer perfluorocarboxylic acids including C17 and C19 to C24 were also found present within a foil sample. Concentrations of 6:2 FTUCA ranged from 0.78 to 127 ng g−1 in methanolic extracts and up to 6 ng g−1 in food simulant after 240 h migration test. These results demonstrate the prevalence of both emerging and legacy PFAS in food packaging samples and highlight the usefulness of non-targeted tools to identify PFAS not included in targeted methods.

In-situ embedding of carbon dots in perovskite GdAlO3:Eu3+/Li+ composite: Boosting phosphor stability, optical thermometry, flexible displays and data protection applications

Phosphors that are highly fluorescent have shown considerable promise in applications like flexible displays and enhancing data security. Still, the task of boosting their fluorescence attributes, especially in the realm of phosphors, remains an ongoing challenge. Precisely, the luminescent properties of GdAlO3:Eu3+ (GAO:Eu3+) phosphors co-doped with lanthanide (Ln) and alkali ions (M+) are successfully synthesized using a solution combustion method. The integration of fluorescent carbon dots (CDs) onto the GAO:7Eu3+/Li+ phosphor surface notably enhanced their luminescent characteristics. Incorporating CDs into GAO:7Eu3+/Li+ resulted in a decrease in both positive and negative defects within the phosphor, consequently enhancing its crystalline structure. Particularly noteworthy is the substantial spectral alignment observed between the emission of CDs and the absorption of GAO:7Eu3+/Li+. When excited by 395 nm UV light, the GAO phosphors displayed the distinctive emission associated with the doping ions. The emission intensity of GAO:7Eu3+/Li+, and CDs(7 wt%)@GAO:7Eu3+/Li+ composite rises by 18 and 66.23 folds, respectively, in comparison to the corresponding samples lacking the inclusion of CDs. The enhanced photoluminescence (PL) intensity observed can be attributed to the Förster resonance energy transfer (FRET) mechanism. In comparison to its emission intensity at room temperature, the CDs@GAO:7Eu3+/Li+ composite retains 95.6% of its intensity, while GAO:7Eu3+ retains 88.5% and GAO:7Eu3+/Li+ retains 91.2% at 400 K, showcasing remarkable thermal stability. The finely optimized CDs(7 wt%)@ GAO:7Eu3+/Li+ combination displays an impressive color purity (CP) of 98.15 %. Furthermore, this NCs demonstrates significant potential for optical thermometry across a broad temperature spectrum ranging from 300 to 480 K. The brush mode is utilized to create anti-counterfeiting (AC) labels using the optimized composite ink on various surfaces. The resulting AC tags exhibit high resolution and durability. The fabricated flexible films exhibit remarkable flexibility, and foldability significantly broaden the scope of potential applications in the field of AC. These results suggest that CDs(7 wt%)@ GAO:7Eu3+/Li+ have potential for multifaceted applications in flexible luminescent films, AC, and optical thermometry.

Microstructure modification in Ba-doped SnO2-based ceramics with promising thermal conductivity and electrical properties

In this paper, the thermal conductivity of Ba-doped SnO2 varistors was tested using the heat flow method, and it was found that the thermal conductivity is related to the grain boundary barrier of the samples. Introducing the reduction of impurity phases and point defects is an effective method to enhance the thermal conductivity of SnO2-based varistors. Energy dispersive spectrograms indicate that the content of spinel Co2SnO4 doped with 1 mol% Ba is the least when the arrester is operated at 40 °C. The positive and negative charge defects are fully compensated, thereby reducing phonon scattering and improving the thermal conductivity of the samples. Spinel Co2SnO4 occupies the position of the effective grain boundary, so the reduction of Co2SnO4 and the compensation of positive and negative defects also effectively increase the grain boundary barrier. When the doping amount of Ba is 1 mol%, the optimal potential barrier height is 1.48eV, the nonlinear coefficient is 45, the leakage current is 0.8 μA/cm2 and the voltage gradient is 418 V/mm.

The role of aspect ratio and activity on how active nematic defects distribute on toroidal surfaces

Active topological defects are one of the most exciting non-equilibrium systems of recent times. In our experiments, we confine an active nematic populated by positive and negative topological defects to a toroidal surface, and explore how the local geometry, parameterised by the Gaussian curvature, influences the distribution of defects. We find curvature-induced defect unbinding, for relatively thick tori and low activities. In contrast, for high activity and thin tori, which serve to locally approach the cylindrical limit, the relevance of the defect-curvature coupling is lost. Overall, our results illustrate how curvature and activity can both be used to affect how defects distribute on surfaces with varying curvature.

Two-dimensional line defect lattice solitons in nonlinear fractional Schrödinger equation

The existence, stability, and propagation dynamics of two-dimensional line defect lattice solitons (LDLSs) in a photorefractive crystal with focusing saturable nonlinearity under fractional diffraction effect are numerically investigated. It is shown that, the LDLSs stability domain narrows with increasing Lévy index in the semi-infinite bandgap either in the negative or positive defect lattice. While in the first bandgap, LDLSs are stable for the negative defect lattice and unstable for the positive defect lattice. Additionally, linear stability analysis indicates that the stability and power of LDLSs depend strongly on the Lévy index, defect depth, and propagation constant in different bandgaps. For LDLSs in the semi-infinite bandgap, the stability can be improved by decreasing either the Lévy index or the negative defect depth.

Zwitterion Dual-Modification Strategy for High-Quality NiOx and Perovskite Films for Solar Cells.

Nickel oxide (NiOx) has been limited in use as a hole transport layer for its low conduction, surface defects, and redox reactions with the perovskite layer. To address these issues, the incorporation of zwitterion L-tryptophan (Trp) is proposed at the NiOx/Trp interface. The carboxyl group of Trp effectively passivates the surface positive defects of NiOx, thereby improving its optical and electrical properties. The ammonium group of Trp not only passivates negative defects but modulates the growth of the perovskite layer, resulting in an improved perovskite film quality. Furthermore, the Trp layer acts as a buffer layer, suppressing adverse interfacial reactions between the perovskite and NiOx. Consequently, perovskite solar cells with 1.56 and 1.68eV absorbers achieve the champion power conversion efficiency(PCE) of 23.79% and 20.41%, respectively. Moreover, the unencapsulated devices demonstrate excellent long-term stability, retaining above 80% of the initial PCE value after 1600 h of storage in the air with a humidity of 50-60%.

Surface passivation properties of atomic-layer deposited hafnium oxide on a (100) β-Ga2O3 MOSFET

We report the effect of HfO2 passivation on the electrical characteristics of (100) β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs). The atomic-layer-deposited HfO2 layer with negative defect charges enhances the transconductance and subthreshold slope. A significant positive threshold voltage (V TH) shift of ∼32 V is induced after the passivation. Moreover, significantly less V TH shift of ∼2 V is observed under negative bias stress (NBS) for 3600 s in comparison with an Al2O3 passivated and unpassivated device. Physics-based technology computer aided design (TCAD) simulation is performed to demonstrate the surface depletion effect and the dependency on the density of negative fixed charges in the HfO2 passivation layer. Finally, the HfO2 passivated device maintains superior electrical characteristics compared to the unpassivated device at a temperature of up to 500 K.

Abstract 15455: Unraveling the Mechanism of Ischemia in Pediatric Patients With R-AAOCA: Fixed and Dynamic Obstruction

Introduction: Although rare, anomalous aortic origin of the right coronary artery (R-AAOCA) is associated with exercise-related sudden cardiac death and dynamic obstruction to coronary flow in the intramural segment has been proposed as the ischemia mechanism. We aim to describe fixed and dynamic obstruction mechanism of ischemia in select group of R-AAOCA patients undergoing invasive transcatheter stress FFR and iFR. Hypothesis: Ischemia in R-AAOCA involves a 2-tier mechanism involving both fixed and dynamic obstruction. Methods: Single institution retrospective study of R-AAOCA patients undergoing cardiac catheterization due to ischemic symptoms and negative perfusion defects on dobutamine stress CMRI. Coronary angiography was performed in all patients. Instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR) were performed at baseline and under pharmacologic stress with adenosine (aFFR)/dobutamine (diFR) when the coronary ostium was engaged in a stable manner. Significant fixed obstruction was considered if aFFR<0.80 and dynamic if diFR <0.85. Results: A total of 14/446 (3%) R-AAOCA patients were included. In 10 patients, a Verrata pressure guide wire (Volcano, San Diego, CA) was able to be advanced to perform iFR and FFR. Fixed RCA obstruction was demonstrated in 4/10 patients (40%) and 2 of these (2/10, 20%) also had dynamic RCA obstruction (Table). All 4 patients were referred to surgery: 3 completed, 1 pending. In 4/14 (28%) patients, iFR and FFR were not performed due to inability to engage the RCA ostium, all of which found to be hypoplastic (1-1.5 mm) and slit-like at surgery. There were no procedural complications. Conclusions: In a small cohort of R-AAOCA patients, mechanisms for myocardial ischemia during stress suggest dynamic and fixed components. Our preliminary results provide important insight for risk stratification. Long-term follow-up will be important to validate the performance of iFR/FFR in R-AAOCA

The Effect of Preloaded Compressive Stress and Curvature of Defect on Blast-Induced Fracture Behavior by Caustic and Numerical Models

In this study, the effects of preloaded uniaxial compressive stress and defect (prefabricated by laser cutting) curvature on blast-induced cracks and stress wave propagation were investigated in polymethyl methacrylate (PMMA) specimens using caustics theory. Based on the mathematical relationship between stress and optics, the fracture behavior (the propagation path, dynamic stress intensity factors (DSIFs), propagation velocity, initiation angle of the main crack, and damage degree between the defect and the blasthole) was calculated and analyzed quantitatively. The results show that the preloaded stress could mainly restrain the main crack propagation in the horizontal direction and reduce the initiation angle and damage degree at the defects. Meanwhile, the crack initiation position of the positive curvature defect was not at the end of the defect. In addition, the curvature of the defect significantly affected the blast-induced fracture compared to preloaded stresses. Comparing the main crack with other curvature defects, the DSIFs, velocity, crack arrest time, crack length, and horizontal offset distance of the main crack with negative curvature defect were the largest. The variation in the full stress field in the specimen under blasting and preloaded stress was simulated by a numerical model. The results show that the curvature of the defect has a significant effect on tensile waves at the end of defects, and the tensile stress from high to low was C-25, C0, and C25, in that order.

Conductive passivating contact for high fill factor monolithic perovskite/silicon tandem solar cells

AbstractPerovskite/silicon tandem solar cells (PK/Si TSCs) blaze the way in pushing power conversion efficiency (PCE) beyond the single‐junction Shockley–Queisser limit. Meanwhile, localized defects in perovskite subcells result in a lower fill factor (FF), which limits further improvement of PCE in PK/Si TSCs. Herein, we report a conductive passivation contact layer by posttreatment of bis(2‐hydroxyethyl)dimethylammonium chloride (BDAC) zwitterion molecule on the perovskite surface. It can passivate the positive and negative localized defects, inhibit the formation of Pb0, and spontaneously convert the perovskite surface to be a more n‐type conductive contact layer for charge separation. These combined enhancements enabled a PCE of 21.4% with an enhanced VOC of 80 mV and an FF of 82.84% for the inverted single‐junction device prepared by the two‐step method. Moreover, BDAC passivation achieved a PCE of 28.67% with an FF of 80.02% for PK/Si TSCs. In addition, the scaling‐up device with an active area of 11.879 cm2 delivers a PCE of 24.46%, and a minimodule with power conversion over 2 W is designed and fabricated.

Tunable charge injection from graphene to halide perovskite induced by reversible ion segregation

Migration of point defects can result in various performance instabilities in organometal halide perovskite devices. In particular, the segregation of charged defects can influence the electron transport, but the correlation between ionic and electronic transports remains elusive. In this work, we use a graphene/methylammonium lead iodide capacitor to probe the effect of ion segregation on the charge injection behavior at the graphene/perovskite junction. In our samples, the ion segregation in the perovskite film is induced by a controllable electric field applied through an electrostatic gate. At the same time, the charge injection from graphene to the perovskite is probed by monitoring changes in the graphene conductivity. It is found that a positive (negative) defect accumulation layer near the graphene/perovskite interface can facilitate electron (hole) injection from the graphene electrode to the perovskite. Because the polarity of the defect accumulation layer is switchable by changing the direction of the applied electric field, the graphene/perovskite interface behaves like a Schottky junction with a tunable charge injection barrier height. This behavior should be generally found in other metal/halide perovskite interfaces as well.

Defect solitons supported by optical lattice with saturable nonlinearity in fractional Schrödinger equation

We address the existence, stability, and propagation dynamics of both one- and two-dimensional defect solitons supported by optical lattice with saturable nonlinearity in fractional Schrödinger equation. Under the influence of fractional effect, in one dimension, solitons exist stably in limited regions in the semi-infinite bandgap with high and low power both for a negative and positive defect lattice. In the first bandgap, solitons are stable for negative defect lattice, while unstable for positive defect lattice. In the second bandgap, only stable solitons can propagate in small regions for the positive defect lattice. With increasing the Lévy index from 1 to 2, the power of the defect solitons decreases in the semi-infinite bandgap and increases in the first bandgap. Linear stability analyses show that, the domains of stability for defect solitons strongly depend on the Lévy index, defect strength and different bandgaps. In two dimension, defect solitons can exist stably at high and moderate power regions in the semi-infinite bandgap and all regions in the first bandgap with negative defect lattice, while they are stable at high, moderate and low power regions in the semi-infinite bandgap and unstable in the first bandgap with positive defect lattice.

The Microwave Rotational Electric Resonance (RER) Spectrum of Benzothiazole.

The microwave spectra of benzothiazole were measured in the frequency range 2-26.5 GHz using a pulsed molecular jet Fourier transform microwave spectrometer. Hyperfine splittings arising from the quadrupole coupling of the 14N nucleus were fully resolved and analyzed simultaneously with the rotational frequencies. In total, 194 and 92 hyperfine components of the main species and the 34S isotopologue, respectively, were measured and fitted to measurement accuracy using a semi-rigid rotor model supplemented by a Hamiltonian accounting for the 14N nuclear quadrupole coupling effect. Highly accurate rotational constants, centrifugal distortion constants, and 14N nuclear quadrupole coupling constants were deduced. A large number of method and basis set combinations were used to optimize the molecular geometry of benzothiazole, and the calculated rotational constants were compared with the experimentally determined constants in the course of a benchmarking effort. The similar value of the χcc quadrupole coupling constant when compared to other thiazole derivatives indicates only very small changes of the electronic environment at the nitrogen nucleus in these compounds. The small negative inertial defect of -0.056 uÅ2 hints that low-frequency out-of-plane vibrations are present in benzothiazole, similar to the observation for some other planar aromatic molecules.

Why Islamic Economics ? The Difference Between The Conventional System And The Islamic Economic System

The presence of an economic system is a real part of the effort to answer the economic problem of what, haw, for whom. Every economic system has different ways and ways of solving these problems. This research aims to answer the main problem, why does it have to be Islamic economics? With the liberal research approach, these problems are discussed starting with data collection based on secondary data in the form of research articles and books related to the main focus of the research. Further data were analyzed using content analysis and comparative descriptive analysis methods. The results of this study indicate that the main reason why an Islamic economic system is needed is that Islamic economics is evident from various historical records starting from the beginning of the Prophet Muhammad. Until now the Islamic economic system is clearly different in answering the economic problems of what, haw, and for whom. The Islamic economic system rests on the principle of values that enable human moral hazard to be minimized by upholding the values of monotheism, justice and balance. While the conventional economic system, capitalism and socialism recorded various negative defects starting from the 1929 crisis, the Subprime Mortgage crisis, the dissolution of the Soviet NEP. The results of this study have implications for strengthening the importance of carrying out economic activities that are based on justice and a balance in life.