Abstract:P-type delafossite CuGaO2 is a wide-bandgap semiconductor for optoelectronic applications, and its lattice parameters are very similar to those of n-type semiconductor wurtzite ZnO. Accordingly, the investigation of crystalline heterostructures of CuGaO2 and ZnO has attracted significant attention. In this study, interfacial CuGaO2/ZnO hetero-compounds were examined through X-ray diffraction (XRD) analysis, confocal micro-Raman spectroscopy, and X-ray photo-electron spectroscopy (XPS). XRD and Raman analysis revealed that the hydrothermal deposition of ZnO on hexagonal platelet CuGaO2 base crystals was successful, and the subsequent reduction process could induce a unique, unprecedented reaction between CuGaO2 and ZnO, depending on the deposition parameters. XPS allowed the comparison of the binding energies (peak position and width) of the core level electrons of the constituents (Cu, Ga, Zn, and O) of the pristine CuGaO2 single crystallites and interfacial CuGaO2/ZnO hybrids. The presences of Cu2+ ions and strained GaO6 octahedra were the main characteristics of the CuGaO2/ZnO hybrid interface. The XPS and modified Auger parameter analysis gave an insight into a specific polarization of the interface, promising for further development of CuGaO2/ZnO hybrids.Keywords: p-type semiconductor; hetero-interface; hydrothermal synthesis; hexagonal platelet hybrids; X-ray photoemission spectroscopy; Raman spectroscopy
Acute ischemic stroke (AIS) is among the leading causes of death and disability in developed countries. Traditional treatment entails the use of anti-coagulants and/or aspirin. Within the appropriate time-window, various endovascular approaches have been employed to manage patients with AIS. Endovascular therapy comprises a number of pharmacological and mechanical procedures. Intravenous (IV) thrombolysis including the use of tissue plasminogen activator (tPA) is an accepted treatment for AIS administered within 3 hours of onset. Mechanical procedures including the use of various micro-guidewires, micro-snares, and retrievers (e.g., the mechanical embolus removal in cerebral ischemia [MERCI] device, the L5 Retriever, and the Penumbra System) offer the promise of effective treatment for patients in whom pharmacological thrombolysis is contraindicated or might be ineffective. Although earlier devices had shown mixed results, better results have been obtained with modern stent retrievers combined with advanced imaging to select patients with viable tissue for rescue.
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In a prospective, observational, cohort study, González et al (2007) evaluated the safety and effectiveness of thrombus extraction using a micro-snare in patients with AIS. Consecutive patients with AIS (less than 6 hours of ischemia for anterior circulation and less than 24 hours for posterior circulation) who had been previously excluded from IV tPA thrombolysis were included and followed-up for 3 months. Mechanical embolectomy with a micro-snare of 2 to 4 mm was undertaken as the first treatment. Low-dose intra-arterial (IA) thrombolysis or angioplasty was used if needed. Thrombolysis in Myocardial Infarction (TIMI) grade and modified Rankin Scale (mRS) score were used to evaluate vessel re-canalization and clinical effectiveness, respectively. A total of 9 patients (mean age of 55 years, range of 17 to 69 years) were included. Their basal mean National Institutes of Health Stroke Scale (NIHSS) score was 16 (range of 12 to 24). In 7 out of the 9 patients (77.8 %) the clot was removed, giving a TIMI grade of 3 (n = 4) and TIMI grade 2 (n = 3). Occlusion sites were: middle cerebral artery (MCA, n = 4), basilar artery (n = 2) and anterior cerebral artery plus MCA (n = 1). The mean time for re-canalization from the start of the procedure was 50 mins (range of 50 to 75 mins). At 3 months, the mRS score was 0 (n = 2) and 3 to 4 (n = 3; 2 patients died). The authors concluded that the micro-snare is a safe procedure for mechanical thrombectomy with a good re-canalization rate. Moreover, they stated that further studies are needed to determine the role of the micro-snare in the treatment of AIS.
Sugiura and colleagues (2008) examined the safety and effectiveness of combined IV recombinant- tPA (r-tPA) and simultaneous endovascular therapy (ET) as primary rather than rescue therapy for hyper-acute MCA occlusion. A total of 29 patients eligible for IV r-tPA, who were diagnosed as having MCA (M1 or M2) occlusion within 3 hours of onset, underwent thrombolysis. In the combined group, patients were treated by IV r-tPA (0.6 mg/kg for 60 mins) and simultaneous ET (intra-arterial r-tPA, mechanical thrombus disruption with micro-guidewire, and balloon angioplasty) initiated as soon as possible. In the IV group, patients were treated by IV r-tPA only. The improvement of the NIHSS score at 24 hrs was 11.0 +/- 4.8 in the combined group versus 5.0 +/- 4.3 in the IV group (p
Shah et al (2009) examined the safety and tolerability of super-selective intra-arterial magnesium sulfate in combination with intra-arterial nicardipine in patients with cerebral vasospasm after SAH. Patients were treated in a prospective protocol at 2 teaching medical centers. Emergent cerebral angiography was performed if there was either clinical, ultrasound, and/or CT perfusion deficits suggestive of cerebral vasospasm. Intra-arterial magnesium sulfate (0.25 to 1 g) was administered via a microcatheter in the affected vessels in combination with nicardipine (2.5 to 20.0 mg). Mean arterial pressures (MAP) and intra-cranial pressures (ICP) were monitored during the infusion. Immediate and sustained angiographic and clinical improvement was determined from post-treatment angiograms and clinical follow-up. Angiographical and clinical outcomes were compared to 2 published case series that has used nicardipine alone. A total of 58 vessels were treated in 14 patients (mean age of 42 years; 11 women) with acute SAH. The treatment was either intra-arterial nicardipine and magnesium sulfate alone or in conjunction with primary angioplasty. Forty vessels (69 %) had immediate angiographical improvement with intra-arterial nicardipine and magnesium sulfate alone and 18 vessels (31 %) required concomitant balloon angioplasty with complete reversal of the vasospasm. Re-treatment was required in 13 vessels (22 %) and the median time for retreatment was 2 days (range of 1 to 13 days). Nicardipine treatment resulted in the reduction of MAP (12.3 mmHg, standard error [SE] 1.34, p
Auboire and colleagues (2018) stated that microbubbles (MBs) combined with ultrasound sonothrombolysis (STL) appeared to be an alternative therapeutic strategy for AIS, but clinical results remain controversial. In a systematic review , these investigators identified the parameters tested; evaluated evidence on the safety and efficacy on pre-clinical data on STL; and examined the validity and publication bias. PubMed and Web of Science databases were systematically searched from January 1995 to April 2017 in French and English. These investigators included studies evaluating STL on animal stroke model. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Data were extracted following a pre-defined schedule by 2 of the authors. The CAMARADES criteria were used for quality assessment. A narrative synthesis was conducted. A total of 16 studies met the inclusion criteria. The result showed that ultrasound parameters and types of MBs were heterogeneous among studies. Numerous positive outcomes on efficacy were found, but only 4 studies demonstrated superiority of STL versus recombinant tPA on clinical criteria. Data available on safety were limited. The authors concluded that further in-vivo studies are needed to demonstrate better safety and efficacy of STL compared to currently approved therapeutic options. Moreover, these researchers stated that the future explorations on the safety of STL are essential. To achieve this objective, animal models, which reproduce the human pathophysiology (i.e., older animals, cardio-vascular risk factors, significant duration of ischemia) should be used. Finally, MRI guidance and cavitation detection have not been evaluated in ischemic stroke yet but their use in STL look promising to guarantee a good safety/efficacy profile.
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