Study of Atomic Layer Deposition Nano-Oxide Films on Corrosion Protection of Al-SiC Composites.

In recent years, aluminum matrix composites (AMCs) have attracted attention due to their promising properties. However, the presence of ceramic particles in the aluminum matrix renders AMCs a high corrosion rate and makes it challenging to use traditional corrosion protection methods. In this study, atomic layer deposition (ALD) techniques were used to deposit HfO2, ZrO2, TiO2, and Al2O3 thin films on AMC reinforced with 20 vol.% SiC particles. Our results indicate that the presence of micro-cracks between the Al matrix and SiC particles leads to severe micro-crack-induced corrosion in Al-SiC composites. The ALD-deposited films effectively enhance the corrosion resistance of these composites by mitigating this micro-crack-induced corrosion. Among these four atomic-layer deposited films, the HfO2 film exhibits the most effective reduction in the corrosion current density of Al-SiC composites in a 1.5 wt% NaCl solution from 1.27 × 10-6 A/cm2 to 5.89 × 10-11 A/cm2. The electrochemical impedance spectroscopy (EIS) investigation shows that HfO2 deposited on Al-SiC composites has the largest Rp value of 2.0 × 1016. The HfO2 film on Al-SiC composites also exhibits effective inhibition of pitting corrosion, remaining at grade 10 even after 96 h of a salt spray test.

Synthetic dysmobility screen unveils an integrated STK40-YAP-MAPK system driving cell migration.

Integrating signals is essential for cell survival, leading to the concept of synthetic lethality. However, how signaling is integrated to control cell migration remains unclear. By conducting a "two-hit" screen, we revealed the synergistic reduction of cell migration when serine-threonine kinase 40 (STK40) and mitogen-activated protein kinase (MAPK) were simultaneously suppressed. Single-cell analyses showed that STK40 knockdown reduced cell motility and coordination by strengthening focal adhesion (FA) complexes. Furthermore, STK40 knockdown reduced the stability of yes-associated protein (YAP) and subsequently decreased YAP transported into the nucleus, while MAPK inhibition further weakened YAP activities in the nucleus to disturb FA remodeling. Together, we unveiled an integrated STK40-YAP-MAPK system regulating cell migration and introduced "synthetic dysmobility" as a novel strategy to collaboratively control cell migration.

Perfusion measures for symptom severity and differential outcome of revascularization in limb ischemia: Preliminary results with arterial spin labeling reactive hyperemia.

BACKGROUND: Previously, a theoretical model based on microvascular physiology was established to facilitate the interpretation of calf perfusion dynamics recorded by arterial spin labeling (ASL). PURPOSE: To investigate the clinical relevance of novel perfusion indices by comparing them to the symptoms, response to revascularization, and short-term functional outcome in patients with peripheral arterial disease (PAD). STUDY TYPE: Prospective cohort study. POPULATION: Nineteen patients with PAD. FIELD STRENGTH/SEQUENCE: Pulsed ASL at 3T. ASSESSMENT: The mid-calf reactive hyperemia induced by 2 minutes of arterial occlusion was recorded in PAD patients. The perfusion responses were characterized by the peak, time-to-peak, and physiological model-derived indices including the baseline perfusion fr , arterial resistance Ra , and compliance Ca , and sensitivity gATP and response time τATP of downstream microvasculature to metabolic stress. These indices were compared to the disease severity and outcome within 6 months after revascularization assessed by self-reported symptoms and the ankle-brachial index. Disease severity was categorized as asymptomatic, claudication, or critical limb ischemia. The outcome was categorized as symptom resolved or limited improvement. STATISTICAL TESTS: Severity and outcome groups were compared using Mann-Whitney and Kruskal-Wallis tests with Holm-Sidak adjustments. RESULTS: The peak perfusion decreased and model arterial resistance increased progressively with increasing severity of limb ischemia (P = 0.0402 and 0.0413, respectively). Eleven patients had a successful endovascular procedure, including six patients who had symptoms resolved, four patients who had remaining leg pain, and one patient lost to follow-up. The subjects with limited improvement had significantly lower preintervention microvascular sensitivity gATP than those with symptoms resolved (8.72 ± 1.46 vs. 4.93 ± 0.91, P = 0.0466). DATA CONCLUSION: ASL reactive hyperemia reflects multiple aspects of the pathophysiology. Measures of macrovascular arterial disease are related to the manifested symptom severity, whereas preintervention gATP associated with microvascular dysfunction is related to prognosis following revascularization. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 4 J. Magn. Reson. Imaging 2018;47:1578-1588.

Magnetic resonance imaging characteristics of lesions relate to the difficulty of peripheral arterial endovascular procedures.

OBJECTIVE: Limitations with current peripheral arterial imaging modalities make selection of patients for percutaneous vascular interventions difficult. The purpose of this study was to determine whether a novel preprocedural magnetic resonance imaging (MRI) method can identify lesions that would be more challenging to cross during percutaneous vascular intervention. METHODS: Fourteen patients with peripheral arterial disease underwent MRI before their intervention. A novel steady-state free precession flow-independent magnetic resonance (MR) angiogram was used to locate lesions, and an ultrashort echo time image was used to characterize hard lesion components including calcium and dense collagen. Lesions were characterized as hard if ≥50% of the lumen was occluded with calcium or collagen (as determined by MR image characteristics) in the hardest cross section within the lesion. The primary outcome was the time it took to cross a guidewire through the target lesion. The secondary outcome was the need for stenting. RESULTS: Of 14 lesions, 8 (57%) were defined as hard and 6 (43%) were soft on the basis of MR image characteristics. Hard lesions took significantly longer to cross than soft lesions (average, 14 minutes 49 seconds vs 2 minutes 17 seconds; P = .003). Hard lesions also required stenting more often than soft lesions (Fisher exact test, P = .008). Of 14 lesions, 2 (14%) could not be crossed with a guidewire, and both lesions were hard. MR images also detected occult patencies and noncalcified hard lesions that could not be seen on X-ray angiography. CONCLUSIONS: MRI can be used to determine which peripheral arterial lesions are more difficult to cross with a guidewire. Future work will determine whether MRI lesion characterization can predict long-term endovascular outcomes to aid in procedure planning.

A physiological model for interpretation of arterial spin labeling reactive hyperemia of calf muscles.

To characterize and interpret arterial spin labeling (ASL) reactive hyperemia of calf muscles for a better understanding of the microcirculation in peripheral arterial disease (PAD), we present a physiological model incorporating oxygen transport, tissue metabolism, and vascular regulation mechanisms. The model demonstrated distinct effects between arterial stenoses and microvascular dysfunction on reactive hyperemia, and indicated a higher sensitivity of 2-minute thigh cuffing to microvascular dysfunction than 5-minute cuffing. The recorded perfusion responses in PAD patients (n = 9) were better differentiated from the normal subjects (n = 7) using the model-based analysis rather than characterization using the apparent peak and time-to-peak of the responses. The analysis results suggested different amounts of microvascular disease within the patient group. Overall, this work demonstrates a novel analysis method and facilitates understanding of the physiology involved in ASL reactive hyperemia. ASL reactive hyperemia with model-based analysis may be used as a noninvasive microvascular assessment in the presence of arterial stenoses, allowing us to look beyond the macrovascular disease in PAD. A subgroup who will have a poor prognosis after revascularization in the patients with critical limb ischemia may be associated with more severe microvascular diseases, which may potentially be identified using ASL reactive hyperemia.

Phosphor-Free InGaN White Light Emitting Diodes Using Flip-Chip Technology.

Monolithic phosphor-free two-color gallium nitride (GaN)-based white light emitting diodes (LED) have the potential to replace current phosphor-based GaN white LEDs due to their low cost and long life cycle. Unfortunately, the growth of high indium content indium gallium nitride (InGaN)/GaN quantum dot and reported LED's color rendering index (CRI) are still problematic. Here, we use flip-chip technology to fabricate an upside down monolithic two-color phosphor-free LED with four grown layers of high indium quantum dots on top of the three grown layers of lower indium quantum wells separated by a GaN tunneling barrier layer. The photoluminescence (PL) and electroluminescence (EL) spectra of this white LED reveal a broad spectrum ranging from 475 to 675 nm which is close to an ideal white-light source. The corresponding color temperature and color rendering index (CRI) of the fabricated white LED, operated at 350, 500, and 750 mA, are comparable to that of the conventional phosphor-based LEDs. Insights of the epitaxial structure and the transport mechanism were revealed through the TEM and temperature dependent PL and EL measurements. Our results show true potential in the Epi-ready GaN white LEDs for future solid state lighting applications.