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Abstract Background Research on factors influencing the outcomes of revision anterior cruciate ligament (ACL) reconstruction is relatively scarce and mostly relies even on reports from a single group. Understanding the factors contributing to the failure of revision ACL reconstruction can provide valuable information for achieving better clinical outcomes and assist in patient counseling before surgery. Therefore, this study aimed to analyze the factors contributing to surgical failure after revision ACL reconstruction. Methods The medical records of consecutive patients who underwent single-bundle revision ACL reconstruction using the transportal technique between 2010 and 2020 and had a minimum follow-up of 2 years were retrospectively reviewed. Eligible patients were classified into two groups on the basis of the presence of surgical failure during the follow-up period (group NF, patients who did not experience surgical failure; group F, patients who experienced surgical failure). In this study, surgical failure after revision ACL reconstruction was defined as meeting any of the following conditions during follow-up: the presence of graft re-tear confirmed by magnetic resonance imaging (MRI), anterior–posterior laxity graded ≥ 2, or rotational laxity graded ≥ 2. A comparative analysis was conducted on demographic data, as well as peri-, intra-, and postoperative data between the groups. Additionally, a regression analysis was performed to investigate factors influencing surgical failure after revision ACL reconstruction. Results A total of 58 patients were included (group NF, 40 patients; group F, 18 patients). In between-group comparisons of demographic, peri-, and intra-operative data, group F exhibited a higher frequency of multiple revision surgeries (P = 0.001), increased preoperative osteoarthritis grade (P = 0.001), and shallower femoral tunnel depth (P = 0.002) compared with group NF. At the final follow-up, group F demonstrated relatively poor clinical outcomes, both subjectively and objectively. Multivariate regression analysis revealed that all variables that showed differences in the preceding comparisons were independent factors affecting surgical failure after revision ACL reconstruction. Conclusions Surgical failure after revision ACL reconstruction can occur in a substantial number of patients, influenced by non-modifiable factors, such as cases corresponding to multiple revision surgery and preoperative osteoarthritis grade, and modifiable factors, such as femoral tunnel depth.

Abstract Background For effective investigation of the developing structure and chemistry of bone, comprehensive studies including compositional analysis can be achieved through the gradual observation from the micro- to nanometer scale via correlative light and electron microscopy (CLEM). This technique is particularly useful considering the complex hierarchical arrangement of bioapatite and collagen fibrils which may vary according to specific bone tissue types (i.e., lamellar bone and woven bone) and different growth stages. Scanning electron microscopy (SEM) accompanied with the attachment of the scanning transmission electron microscopy (STEM) detector, referred to as the STEM-in-SEM can be utilized to produce high contrast images from materials composed of light elements, and efficiently allows the selection of suitable accelerating voltage for energy-dispersive spectroscopy (EDS). This study aims to emphasize the efficacy of CLEM techniques through applying STEM-in-SEM and EDS analyses, and its application to comparative murine bone investigation in differing ontogenetic stages. Findings We have designed a new grid-holder which can be used for both light and electron microscopy, and we presented an imaging technique for TEM specimens via reflective light microscopy (RLM). For performing CLEM, ultra-thin-sections (UTS) prepared from the femoral bones of 1- to 16-week old of Sprague-Dawley (SD) rats provided light and electron micrographs that can be correlated based on the regions of interest (ROIs). STEM-in-SEM micrographs revealed information not attainable by secondary electron (SE) and back-scattered electron (BSE) micrographs. In addition, for analyzing chemical variation according to growth and development of femoral bones from 1- to 16-week-old rats, comparative chemical analysis was performed through STEM-in-SEM EDS with two reference materials. Conclusion Herein, from femoral bones of SD rats, we have confirmed the rapid chemical and structural variations within the first 8 weeks after birth. STEM-in-SEM micrographs revealed the bone development process of the early stage porous bone matrix subsequently being filled with collagen fibrils and bioapatite. In addition, chemical analysis for carbon and oxygen showed the ratios of inorganic to organic phases according to growth and progress in bone mineralization. As a result, we were able to postulate the growth mechanism of murine femoral bone in the neonatal stages of development. We also anticipate that our CLEM techniques can be further utilized for more thorough investigation of bone structure and chemistry in diverse scales.

Abstract The low-frequency Raman signals of single-wall carbon nanotubes (SWNTs), appearing in the range of 100–300 cm−1, have been interpreted as radial-breathing mode (RBM) comprising pure radial Eigenvectors. Here, we report that most of the low-frequency and intermediate-frequency signals of SWNTs are radial-tangential modes (RTMs) coexisting radial and tangential Eigenvectors, while only the first peak at the low-frequency side is the RBM. Density functional theory simulation for SWNTs of ~ 2 nm in diameter shows that dozens of RTMs exhibit following the RBM (~ 150 cm−1) up to G-mode (~ 1592 cm−1) in order with Landau regulation. We specify the RBM and the RTM on Raman spectra obtained from SWNTs, where both appear as prominent peaks between 149 and 170 cm−1 and ripple-like peaks between 166 and 1440 cm−1, respectively. We report that the RTMs have been regarded as RBM (~ 300 cm−1) and ambiguously named as intermediate-frequency mode (300–1300 cm−1) without assignment. The RTMs gradually interlink the RBM and the G-mode resulting in the symmetric Raman spectra in intensity. We reveal high-resolution transmission microscope evidence for a helical structure of SWNTs, informing the typical diameter of commercial SWNTs to be 1.4–2 nm.

Abstract Background In a transmission electron microscope (TEM), the objective lens (OL) is the most important component because the first image and diffraction pattern for a specimen are formed by applying a specific OL current and specimen height (SH). In TEM, the focal length of the OL should be controlled independently of the specimen position. Therefore, the initial conditions for OL should be determined by selecting the optimum imaging condition of the specimen based on the OL current and the specimen position. We would like to present a method for finding the optimal imaging condition for OL that can be applied to conventional or low-resolution TEM where high-resolution (HR) imaging is impossible. Findings We conducted an abnormal contrast imaging experiment using Au nanoparticles (AuNPs). Abnormal contrast imaging was obtained by artificially controlling the mechanical alignment of OL P/Ps. Abnormal contrasts (shadow contrasts) of AuNPs were observed in all images obtained for various SH and OL currents. It was confirmed that these shadow contrasts of AuNPs result from the parasitic aberration caused by imperfect mechanical alignment of the OL P/Ps. From the quantitative analysis of the images, it was found that the effects of parasitic aberration in the TEM images decreased as SH approached the optimal position in the OL P/P. Conclusion We examined the relationship of SH and OL current using the abnormal contrast imaging technique. The standard OL current and optimal SH were determined with OL condition minimizing the shadow contrast of images. The experimentally determined optimal SH at standard OL current in our specially designed OL system differed from that of the well-known asymmetry OL system. Therefore, it is essential to examine the optimum conditions from a practical perspective. Consequently, our abnormal contrast imaging method, which can be analyzed even in conventional imaging without HR-TEM performance, can help optimize the OL conditions during the manufacturing stage of the TEM instrument.

AAh boron nitride (BN) crystal, assigned to an orthorhombic space group (No. 31, Pm21), is reported here. This new AAh BN crystal exhibits a `linear' morphology for high-resolution transmission electron microscopy (HRTEM) and a (non-hexagonal) `diagonal' electron-diffraction pattern, which have been experimentally demonstrated in this article. It is also demonstrated that this new crystal is the basic structure of multi-walled BN nanotubes (BNNTs) existing in the form of a helix. The helical AAh BNNTs exist in a metastable phase owing to 〈200〉 texture growth of the orthorhombic crystal, where the energy is ∼15 meV higher than that of stable AB or AA′ BN. It is shown that the typical scanning electron microscope `fluffy cotton-like' morphology of BNNTs is due to secondary growth of diverse BN sheets (including mono-layers) on incoherently scrolled wall strands of BNNTs, providing further evidence for the helical structure with HRTEM evidence for a left-handed helix.

Abstract Background The contrast transfer function (CTF) is an important principle in the field of transmission electron microscopy (TEM) imaging. It provides information on how the electron wave that interacted with a sample (in frequency domain) in an objective lens is transferred to the imaging system (in real space domain) depending on the effects of lens aberrations. Based on the CTF calculation, various useful results, such as the TEM instrumental information limit and optimal imaging condition, can be estimated. Recently, aberration-corrected TEM (AC-TEM) has been widely applied in various research fields for imaging at the nanoscale or atomic scale. To use AC-TEM effectively, a deep understanding of the complicated CTF with an electron wave controlled via an aberration corrector is required. Unfortunately, this complicated CTF is difficult to understand for most microscopists without the use of computational tools. In this study, we develop the extended CTF (exCTF) simulator to perform the full as well as simple CTF calculation. Findings We successfully developed the exCTF simulator, which can obtain more information than previously reported software. The exCTF simulator not only calculates the CTF for basic optical information that can be obtained in conventional TEM, but also can calculate the extended CTF with various aberrations (up to fifth order) for more detailed information obtained in advanced high-performance AC-TEM in one-dimensional and two-dimensional formats. The user interface of the simulator includes CTF calculation, saving, and edit functions for five graphs for different conditions, allowing for detailed comparative analysis. Conclusion We confirmed that the exCTF simulator produced reliable calculation data for various applications. The exCTF simulator made it easy to obtain instrumental performance information and demonstrated the influence of optical aberrations on the actual resolution of AC-TEM. Consequently, the proposed exCTF simulator is expected to be useful to microscopists as a simulation tool for electron microscopy and as a training tool for electron optics.

The increased use of plastics has seen the emergence of microplastics, which have become progressively more problematic. Although many degradation studies have been conducted to address the problem of microplastics, their impact has not been significant, and much time has been consumed. In this study, low-density polyethylene (LDPE) was degraded using a dielectric barrier discharge (DBD) plasma under various electrical conditions. The experimental results showed that after 120 min of treatment, the removal efficiency reached 5.44%, the carbonyl index (CI) was 1.7308, and the O/C ratio was 0.028. The degree of degradation shown in previous studies was achieved rapidly, and experimental results showed that the degree of LDPE degradation and energy yield was proportional to the voltage and frequency—more specifically, the degree of LDPE surface and internal degradation differed, which should be considered in terms of reducing the extent of mass loss. The results of this study should be helpful for future studies on microplastic degradation using DBD techniques.

Abstract Background With the application of the scanning transmission electron microscopy (STEM) detector, transmitted electron images similar to transmission electron microscopy (TEM) can be obtained from scanning electron microscopy (SEM), which is referred to STEM-in-SEM imaging. Compared to TEM-energy dispersive spectroscopy (EDS), SEM-EDS is expected to be more efficient and reliable for chemical analysis of TEM specimens due to the larger sample space in SEM and the higher take-off angle of the SEM-EDS detector. Unfortunately, this advantage is not well applied to TEM specimens in practice, mainly because of fault signals generated from the commercial grid holders used in SEM and STEM-in-SEM. This study is designed to solve this problem by modifying the commercial holders and to test them through EDS analysis of apatite phases. Findings We first changed the way of assembling parts of the commercial multi-grid holder for SEM. This new assembly was capable of producing a thinner upper cover part, resulting in the reduction of the EDS fault signals generated from the holder. Furthermore, the thin upper part allowed us to get images in shorter working distances, that is, at higher magnifications. This design concept was also applied to the commercial single-grid holder for STEM-in-SEM, producing a new multi-grid holder to be used for loading multiple samples. Conclusion We confirmed that the new holders produced reliable chemical data from apatite phases. In case of oxygen analysis, despite of low electron brightness from the tungsten source, 5 kV provided more stable acquisition and signal yields than 15 kV. We expect that these modified holders facilitate more efficient EDS analysis for multiple samples under the same analytical conditions in SEM and STEM-in-SEM.

Venetoclax, a BCL-2 inhibitor used to treat certain hematological cancers, exhibits low oral bioavailability and high interpatient pharmacokinetic variability. Venetoclax is commonly administered with prophylactic antifungal drugs that may result in drug interactions, of which the underlying mechanisms remain poorly understood. We hypothesized that antifungal drugs may increase venetoclax exposure through inhibition of both CYP3A-mediated metabolism and OATP1B-mediated transport. Pharmacokinetic studies were performed in wild-type mice and mice genetically engineered to lack all CYP3A isoforms, or OATP1B2 that received venetoclax alone or in combination with ketoconazole or micafungin. In mice lacking all CYP3A isoforms, venetoclax AUC was increased by 1.8-fold, and pretreatment with the antifungal ketoconazole further increased venetoclax exposure by 1.6-fold, despite the absence of CYP3A. Ensuing experiments demonstrated that the deficiency of OATP1B-type transporters is also associated with increases in venetoclax exposure, and that many antifungal drugs, including micafungin, posaconazole, and isavuconazole, are inhibitors of this transport mechanism both in vitro and in vivo. These studies have identified OATP1B-mediated transport as a previously unrecognized contributor to the elimination of venetoclax that is sensitive to inhibition by various clinically-relevant antifungal drugs. Additional consideration is warranted when venetoclax is administered together with agents that inhibit both CYP3A-mediated metabolism and OATP1B-mediated transport.

Abstract Background In order to improve the reliability of the electron tomography (ET) technique, which reveals three-dimensional information of nanostructured materials from a series of tilted two-dimensional images, it is essential that the mechanical tilt angle be accurately measured by the transmission electron microscopy (TEM) goniometer. Findings In this study, a calibration specimen was fabricated by nanohole patterning using a focused ion beam in order to determine mechanical tilt angles. The TEM goniometer tilt-angle accuracies were directly confirmed by measuring the changing areas of the projected nanosized hole. New calibration equations were developed and applied for the accurate determination of tilt angle. Conclusion We expect that the calibration specimen will effectively determine and correct the mechanical tilt angles in TEM goniometers leading to improvements in the ET technique.

Graphitic carbon anodes have long been used in Li ion batteries due to their combination of attractive properties, such as low cost, high gravimetric energy density, and good rate capability. However, one significant challenge is controlling, and optimizing, the nature and formation of the solid electrolyte interphase (SEI). Here it is demonstrated that carbon coating via chemical vapor deposition (CVD) facilitates high electrochemical performance of carbon anodes. We examine and characterize the substrate/vertical graphene interface (multilayer graphene nanowalls coated onto carbon paper via plasma enhanced CVD), revealing that these low-tortuosity and high-selection graphene nanowalls act as fast Li ion transport channels. Moreover, we determine that the hitherto neglected parallel layer acts as a protective surface at the interface, enhancing the anode performance. In summary, these findings not only clarify the synergistic role of the parallel functional interface when combined with vertical graphene nanowalls but also have facilitated the development of design principles for future high rate, high performance batteries.

Space-charges in polycrystalline materials can drive segregation of dopants, however an in-depth understanding of this process is still missing. Here, the authors show that in polycrystalline perovskites the space-charge segregation and interfacial structure are nearly identical irrespective of the interface type.

Developing high-performance hybrid energy storage devices requires improved understanding of the mechanism that governs the electrochemical reactions. Here, the authors show the atomic-level working process of cobalt hydroxide electrode for pseudocapacitors.

Crystalline polymers with functionalities along the backbone can store and transfer electrons, ions and gases and thus can be used in devices. However, the formation of such materials can be difficult. Here, Lee and others have produced highly crystalline conjugated polymers via two-monomer-connected precursors.

Recently, eco-friendly energy conversion policies have been being promoted through de-nuclearization and de-coal. For this purpose, a super grid should be built to optimize sustainable renewable energy resources such as solar and wind power. Accordingly, considering the various problems such as technology and cost, a system for efficient energy transmission is required. Hence, research is being actively conducted to apply it, owing to the development of the high voltage direct current (HVDC) system. Among HVDC systems, the cable system is extremely important, in addition to the measurement of the dielectric breakdown strength, space charge, and volume resistivity of insulating materials. The existing resistivity measurement method measures both the volume and surface resistivity using a three-terminal electrode that is used in the international standards of American Society for Testing and Materials (ASTM) D 257 and International Electrotechnical Commission (IEC) 60093. However, the circuit configuration differs depending on the measurement of the volume and surface resistivity; moreover, when a DC voltage is applied to the insulator, a charging current flows and there are multiple samples to be measured, which takes a considerable amount of time. Therefore, in this study, we proposed a new type of resistivity measurement system that is based on the existing three-terminal electrode system. Furthermore, we produced a system capable of simultaneously measuring the volume and surface resistivity. Finally, using this system, we compared and analyzed the volume and surface resistivity of five insulating materials.

[This corrects the article DOI: 10.1371/journal.pone.0186600.].

We have applied correlative microscopy to identify the key constituents of a dorsal rib fossil from Koreanosaurus boseongensis and its hosting mudstone discovered at the rich fossil site in Boseong, South Korea, to investigate the factors that likely contributed to diagenesis and the preservation of fossil bone. Calcite and illite were the commonly occurring phases in the rib bone, hosting mudstone, and the boundary region in-between. The boundary region may have contributed to bone preservation once it fully formed by acting as a protective shell. Fluorapatite crystals in the rib bone matrix signified diagenetic alteration of the original bioapatite crystals. While calcite predominantly occupied vascular channels and cracks, platy illite crystals widely occupied miniscule pores throughout the bone matrix. Thorough transmission electron microscopy (TEM) study of illite within the bone matrix indicated the solid-state transformation of 1M to 2M without composition change, which was more evident from the lateral variation of 1M to 2M within the same layer. The high level of lattice disordering of 2M illite suggested an early stage of 1M to 2M transformation. Thus, the diagenetic alteration of both apatite and illite crystals within the bone matrix may have increased its overall density, as the preferred orientation of apatite crystals from moderate to strong degrees was evident despite the poor preservation of osteohistological features. The combined effects of rapid burial, formation of a boundary region, and diagenesis of illite and apatite within the bone matrix may have contributed to the rib bone preservation.

We succesfully determined the 3D crystal structure of inorganic nano-crystalline material using fast fourier transform (FFT) data from high-resolution electron microscopy (HREM) images. For extracting the reliable structure information from nano-crystalline materials by HREM imaging, it is essential to minimize the dynamical scattering effects happend from interactions bewteen electrons and matters. To alleviate this restriction, we tried to solve the crystal structure by employing high voltage electron microscope (HVEM) which has excellent tilting capability, atomic resolution as well as higher penetration power. First, the allowed sample thickness for CaMoO4 crystal was evaluated by examining the existence of forbidden reflections in FFT data of HREM images obtained at various sample thickness. The kinematical scattering conditions were satisfied up to a sample thickness of about 28.2 nm. Next, we tried to extract the crystallographic data and determine the atomic structure of CaMoO4 crystal by FFT analysis of HREM images obtained from 15 different zone axes. Consequently, its cell parameters and space group were a = 5.24(3) Å, c = 11.50(8) Å and I41/a (#88), respectively. These values were coincided with X-ray crystallography results within 0.002 ~ 0.080 Å. Finally, the atomic structure could be determined with an accuracy of 0.16 Å.

We chracterized the structure properties of two types of ZnS nanocrystals by electron crystallography. X-ray diffraction analysis for these ZnS nanocrystals was performed to determine their initial structures. Their crystallite sizes were about 5.9 nm and 8.1 nm and their crystal systems were hexagonal and cubic, respectively. Their atomic structures, however, could not be determined because of the weak diffraction intensities as well as the unexpected intensities from impurty. To overcome these problems, the structures of ZnS nanocrystals were resolved by electron crystallography using EF-EPD (energy-filtered electron powder diffraction) and HRTEM (high resolution transmission electron microscopy) methods. The structrues determined by Rietveld analysis are P63mc (a = 3.8452 Å, c = 18.5453 Å) and F-43m (a = 5.4356 Å), respectively. Their crystallite shapes were nanorods and quasi-nanoparticles and the nanorod crystal were grown along the [001] direction. It was revealed that the phase transformation between the cubic sphalerite to the hexagonal wurtzite structure of ZnS nanocrytals was related to their shapes and growth mechanism. Electron cryststallogrpahy, employing EF-EPD and HRTEM methods together, has advantages for structure analysis and property chracterization of nano-sized materials.

Much research has been done to reduce dislocation densities for the growth of GaN on sapphire, but has paid little attention to the elastic behavior at the GaN/sapphire interface. In this study, we have examined effects of the addition of Si to a sapphire substrate on its elastic property and on the growth of GaN deposit. Si atoms are added to a c-plane sapphire substrate by ion implantation. The ion implantation results in scratches on the surface, and concomitantly, inhomogeneous distribution of Si. The scratch regions contain a higher concentration of Si than other regions of the sapphire substrate surface, high-temperature GaN being poorly grown there. However, high-temperature GaN is normally grown in the other regions. The GaN overlayer in the normally-grown regions is observed to have a lower TD density than the deposit on the bare sapphire substrate (with no Si accommodated). As compared with the film on an untreated, bare sapphire, the cathodoluminescence defect density decreases by 60 % for the GaN layer normally deposited on the Si-ion implanted sapphire. As confirmed by a strain mapping technique by transmission electron microscopy (geometric phase analysis), the addition of Si in the normally deposited regions forms a surface layer in the sapphire elastically more compliant than the GaN overlayer. The results suggest that the layer can largely absorb the misfit strain at the interface, which produces the overlayer with a lower defect density. Our results highlight a direct correlation between threading-dislocation density in GaN deposits and the elastic behavior at the GaN/sapphire interface, opening up a new pathway to reduce threading-dislocation density in GaN deposits.

139La broadline NMR and HRTEM is used in order to unveil the interplay between local Jahn-Teller (JT) lattice distortions and the magnetic structure in the La1-xCaxMnO3 family of manganites. By increasing x, i.e. diluting the JT active Mn3+ ions, a variety of novel phases is observed, with most spectacular the low T solitonic (stripe) spin arrangement for x≥0.5.