Nonlinear Ultrasonic C-Scan Imaging for Contact-Type Defects in Diffusion-Bonded Joints-A Case Study.

Diffusion bonding technology is widely used in the connection of precision components, yet accurately and reliably detecting contact-type defects on the bond interface still remains a significant problem. Nonlinear ultrasonic methods have been proven to be sensitive to contact-type defects; however, the use of continuous wave or tone burst wave excitation limits its wider application. In this paper, dual-probe nonlinear ultrasonic testing with pulse wave excitation is proposed to detect contact-type defects in diffusion-bonded joints. A titanium alloy diffusion-bonded specimen with artificial defects was fabricated, and the corresponding detection device was designed based on the existing ultrasonic C-scan testing system. A C-scan imaging program based on nonlinear parameters was developed by extracting the fundamental and second harmonic waves of the reflection echo on the bond interface. The results demonstrated that the proposed detection scheme can obtain the nonlinear parameters of diffusion-bonded interfaces, and the nonlinear ultrasonic C-scan image of the bond interface is also obtained. The nonlinear parameter in the contact-type defects areas calculated from the bond interface echo is about 10 times (20 dB) higher than that in macro defects areas, whose gap is about 10 µm. The results indicate that the nonlinear ultrasonic methods seem to be more sensitive to contact-type defects and have a great potential to complement the insufficient detection capability of linear ultrasound for diffusion-bonded joints.

Assessing intra- and inter-molecular charge transfer excitations in non-fullerene acceptors using electroabsorption spectroscopy.

Organic photovoltaic cells using Y6 non-fullerene acceptors have recently achieved high efficiency, and it was suggested to be attributed to the charge-transfer (CT) nature of the excitations in Y6 aggregates. Here, by combining electroabsorption spectroscopy measurements and electronic-structure calculations, we find that the charge-transfer character already exists in isolated Y6 molecules but is strongly increased when there is molecular aggregation. Surprisingly, it is found that the large enhanced charge transfer in clustered Y6 molecules is not due to an increase in excited-state dipole moment, Δµ, as observed in other organic systems, but due to a reduced polarizability change, Δp. It is proposed that such a strong charge-transfer character is promoted by the stabilization of the charge-transfer energy upon aggregation, as deduced from density functional theory and four-state model calculations. This work provides insight into the correlation between molecular electronic properties and charge-transfer characteristics in organic electronic materials.

Push-Pull Heptamethines Near the Cyanine Limit Exhibiting Large Quadratic Electro-Optic Effect.

Harnessing the quadratic electro-optic (QEO) of near-infrared polymethine chromophores over broad telecom wavelength bands is a subject of immense potential but remains largely under-investigated. Herein a series of push-pull heptamethines containing the tricyanofuran (TCF) acceptors and indoline or benzo[e]indoline donors are reported. These dipolar chromophores can attain a highly delocalized "cyanine-like" electronic ground state in solvents spanning a wide range of polarities, in some cases even closer to the ideal polymethine state than symmetrical cyanines. A transmission-mode electromodulation spectroscopy is used to study the electric-field-induced changes in optical absorption and refraction of polymer films doped with heptamethine chromophores, and large and thermally stable QEO effect with high efficiency-loss figure-of-merits that compare favorably to those from dipolar polyenes in poled or unpoled polymers and III-V semiconductors is obtained. The study opens a path for developing organic materials based on cyanine-like merocyanines for complementary metal oxide semiconductor -compatible, fast, efficient, and low-loss electro-optic modulation.

Intravascular Ultrasound Guided Intervention in Calcified Coronary Lesions Showed Good Clinical Outcomes during One Year Follow-Up.

BACKGROUND: Calcified coronary lesions can cause stent under-expansion, malapposition, and polymer degradation, hence increasing the risk of adverse clinical outcomes. Percutaneous coronary intervention (PCI) guided by intravascular ultrasound (IVUS) has been used regularly to improve outcomes. Our primary aim was to evaluate the clinical efficacy of IVUS-guided PCI in calcified coronary lesions. METHODS: From August 2018 to December 2021, we prospectively included 300 patients in the CAPIRO study (CAlcified plaque in patients receiving Resolute Onyx®) at three educational hospitals in Jeonbuk Province. We studied 243 patients (265 lesions) who were followed up for over a year. Based on coronary calcification by IVUS analysis, the patient population was categorized into two groups (Group I: non/mild calcification; Group II: moderate/severe calcification (maximum calcium arc >180° and calcium length > 5 mm)). One-to-one Propensity Score Matching was used to match the baseline characteristics. The stent expansion rate was analyzed by recent criteria. The primary clinical outcome was Major Adverse Cardiac Events (MACE), which included Cardiac death, Myocardial Infarction (MI), and Target Lesion Revascularization (TLR). RESULTS: After follow-up time, the MACE rate in Group I was 1.99%, comparable to Group II's 1.09% (p = 0.594). The components of MACE did not significantly differ between the two groups. Based on absolute MSA or MSA/MVA at MSA site criteria, the stent expansion rate in Group II was lower than that of Group I. Nevertheless, based on recent relative criteria, the stent expansion rate in both groups was comparable. CONCLUSIONS: After more than a year of follow-up, IVUS-guided PCI in moderate/severe calcification lesions was associated with good clinical outcomes, which was comparable with non/mild calcification lesions. Future studies with a larger sample size and a more extended follow-up period are required to clarify our findings.

Architecturally simple organic photodiodes with highly competitive figures of merit via a facile self-assembly strategy.

Photodetectors (PDs) based on organic materials exhibit potential advantages such as low-temperature processing, and superior mechanical properties and form factors. They have seen rapid strides toward achieving performance metrics comparable to inorganic counterparts. Here, a simplified device architecture is employed to realize stable and high-performance organic PDs (OPDs) while further easing the device fabrication process. In contrast to the sequential deposition of the hole blocking layer (HBL) and active layer (conventional 'two-step' processing), the proposed strategy forms a self-assembled HBL and active layer in a 'single-step' process. A high-performance UV-Vis-NIR OPD based on the PM6:BTP-eC9 system is demonstrated using this cost-effective processing strategy. The green solvent processed proof-of-concept device exhibits remarkable responsivity of ∼0.5 A W-1, lower noise current than conventional two-step OPD, ultrafast rise/fall times of 1.4/1.6 µs (comparable to commercial silicon diode), and a broad linear dynamic range of 140 dB. Importantly, highly stable (light and heat) devices compared to those processed by the conventional method are realized. The broad application potential of this elegant strategy is proven by demonstrating the concept in three representative systems with broadband sensing competence.

Poor Prognosis of Contrast-Induced Nephropathy during Long Term Follow Up.

Contrast-induced nephropathy (CIN) is known to associate with poor prognosis. However, there have been few studies for long-term follow up. The purpose of this study was to know the prognosis of CIN during a 10-year follow up. We retrospectively analyzed 528 patients who underwent coronary angiography in Jeonbuk National University Hospital (South Korea, Jeonju) between Jan 2005 to Dec 2006. We excluded the patients who required regular dialysis before study enrollment. We compared adverse events in the no CIN (group I, n=485, 61.9±11.4 years, male 64.1%) and CIN (group II, n=43, 65.7±11.1 years, male 62.8%). Baseline clinical characteristics and cardiovascular risk factors were not different between the two groups except the post-procedure creatinine level (1.04 mg/dL vs 1.84 mg/dL, p=0.0001). The higher rates of all-cause death were observed in group II at 1-year (3.7% vs 13.9%, log-rank, p=0.001), 5-years (17.9% vs 34.9%, log-rank, p=0.003), and 10-years (25.3% vs 48.8%, log-rank, p=0.000). MACE was higher in group II at 1-year (3.9% vs 11.6%, log-rank, p=0.013), 5-years (6.8% vs 20.9%, log-rank, p=0.000) and 10-years (13.4% vs 27.9%, log-rank, p=0.000). In addition, CIN was an independent predictor for 10-year MACE (adjusted HR 3.432, 95% CI 1.314-8.965, p=0.012) after propensity score matching. The worse prognosis of CIN was continuously observed after the 10-year follow-up. Our data suggests that it is worthwhile to prevent the appearance of CIN in order to improve longterm results.

Recent Updates of Lipoprotein(a) and Cardiovascular Disease.

In recent years, epidemiological studies, genome-wide association studies, and Mendelian randomization studies have shown a strong association between increased levels of lipoproteins and increased risks of coronary heart disease and cardiovascular disease (CVD). Although lipoprotein(a) [Lp(a)] was an independent risk factor for ASCVD, the latest international clinical guidelines do not recommend direct reduction of plasma Lp(a) concentrations. The main reason was that there is no effective clinical medicine that directly lowers plasma Lp(a) concentrations. However, recent clinical trials have shown that proprotein convertase subtilisin/kexin-type 9 inhibitors (PCSK9) and second-generation antisense oligonucleotides can effectively reduce plasma Lp(a) levels. This review will present the structure, pathogenicity, prognostic evidences, and recent advances in therapeutic drugs for Lp(a).

A generalized Stark effect electromodulation model for extracting excitonic properties in organic semiconductors.

Electromodulation (EM) spectroscopy, a powerful technique to monitor the changes in polarizability p and dipole moment u of materials upon photo-excitation, can bring direct insight into the excitonic properties of materials. However, extracting Δp and Δu from the electromodulation spectrum relies on fitting with optical absorption of the materials where optical effect in different device geometries might introduce large variation in the extracted values. Here, we demonstrate a systematic electromodulation study with various fitting approaches in both commonly adopted reflection and transmission device architectures. Strikingly, we have found that the previously ascribed continuum state threshold from the deviation between the measured and fitting results is questionable. Such deviation is found to be caused by the overlooked optical interference and electrorefraction effect. A generalized electromodulation model is proposed to incorporate the two effects, and the extracted Δp and Δu have excellent consistency in both reflection and transmission modes in all organic film thicknesses.

On the degradation mechanisms of quantum-dot light-emitting diodes.

The operating lifetime of blue quantum-dot light-emitting diodes (QLED) is currently a short slab for this emerging display technology. To pinpoint the origin of device degradation, here we apply multiple techniques to monitor the electric-field distribution and space-charge accumulation across the multilayered structure before and after lifetime tests. Evident by charge-modulated electro-absorption and capacitance-voltage characteristics, the excited electrons in blue quantum dots (QD) are prone to cross the type II junction between the QD emission layer and the electron-transporting layer (ETL) due to the offset of conduction band minimum, leading to space-charge accumulation and operating-voltage rise in the ETL. Therefore, unlike those very stable red devices, of which the lifetime is primarily limited by the slow degradation of hole-transporting layer, the poor lifetime of blue QLED originates from the fast degradation at the QD-ETL junction. Materials engineering for efficient electron injection is prerequisite for the boost of operating lifetime.

Probing the Energy Level Alignment and the Correlation with Open-Circuit Voltage in Solution-Processed Polymeric Bulk Heterojunction Photovoltaic Devices.

Energy level alignment at the organic donor and acceptor interface is a key to determine the photovoltaic performance in organic solar cells, but direct probing of such energy alignment is still challenging especially for solution-processed bulk heterojunction (BHJ) thin films. Here we report a systematic investigation on probing the energy level alignment with different approaches in five commonly used polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM) BHJ systems. We find that by tuning the weight ratio of polymer to PCBM the electronic features from both polymer and PCBM can be obtained by photoemission spectroscopy. Using this approach, we find that some of the BHJ blends simply follow vacuum level alignment, but others show strong energy level shifting as a result of Fermi level pinning. Independently, by measuring the temperature-dependent open-circuit voltage (VOC), we find that the effective energy gap (Eeff), the energy difference between the highest occupied molecular orbital of the polymer donor (EHOMO-D) and lowest unoccupied molecular orbital of the PCBM acceptor (ELUMO-A), obtained by photoemission spectroscopy in all polymer:PCBM blends has an excellent agreement with the extrapolated VOC at 0 K. Consequently, the photovoltage loss of various organic BHJ photovoltaic devices at room temperature is in a range of 0.3-0.6 V. It is believed that the demonstrated direct measurement approach of the energy level alignment in solution-processed organic BHJ will bring deeper insight into the origin of the VOC and the corresponding photovoltage loss mechanism in organic photovoltaic cells.