Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method

Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-μm thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate

Tirofiban for Stroke without Large or Medium-Sized Vessel Occlusion

The effects of the glycoprotein IIb/IIIa receptor inhibitor tirofiban in patients with acute ischemic stroke but who have no evidence of complete occlusion of large or medium-sized vessels have not been extensively studied. In a multicenter trial in China, we enrolled patients with ischemic stroke without occlusion of large or medium-sized vessels and with a National Institutes of Health Stroke Scale score of 5 or more and at least one moderately to severely weak limb. Eligible patients had any of four clinical presentations: ineligible for thrombolysis or thrombectomy and within 24 hours after the patient was last known to be well; progression of stroke symptoms 24 to 96 hours after onset; early neurologic deterioration after thrombolysis; or thrombolysis with no improvement at 4 to 24 hours. Patients were assigned to receive intravenous tirofiban (plus oral placebo) or oral aspirin (100 mg per day, plus intravenous placebo) for 2 days; all patients then received oral aspirin until day 90. The primary efficacy end point was an excellent outcome, defined as a score of 0 or 1 on the modified Rankin scale (range, 0 [no symptoms] to 6 [death]) at 90 days. Secondary end points included functional independence at 90 days and a quality-of-life score. The primary safety end points were death and symptomatic intracranial hemorrhage. A total of 606 patients were assigned to the tirofiban group and 571 to the aspirin group. Most patients had small infarctions that were presumed to be atherosclerotic. The percentage of patients with a score of 0 or 1 on the modified Rankin scale at 90 days was 29.1% with tirofiban and 22.2% with aspirin (adjusted risk ratio, 1.26; 95% confidence interval, 1.04 to 1.53, P = 0.02). Results for secondary end points were generally not consistent with the results of the primary analysis. Mortality was similar in the two groups. The incidence of symptomatic intracranial hemorrhage was 1.0% in the tirofiban group and 0% in the aspirin group. In this trial involving heterogeneous groups of patients with stroke of recent onset or progression of stroke symptoms and nonoccluded large and medium-sized cerebral vessels, intravenous tirofiban was associated with a greater likelihood of an excellent outcome than low-dose aspirin. Incidences of intracranial hemorrhages were low but slightly higher with tirofiban

Methylprednisolone as Adjunct to Endovascular Thrombectomy for Large-Vessel Occlusion Stroke

Importance It is uncertain whether intravenous methylprednisolone improves outcomes for patients with acute ischemic stroke due to large-vessel occlusion (LVO) undergoing endovascular thrombectomy. Objective To assess the efficacy and adverse events of adjunctive intravenous low-dose methylprednisolone to endovascular thrombectomy for acute ischemic stroke secondary to LVO. Design, Setting, and Participants This investigator-initiated, randomized, double-blind, placebo-controlled trial was implemented at 82 hospitals in China, enrolling 1680 patients with stroke and proximal intracranial LVO presenting within 24 hours of time last known to be well. Recruitment took place between February 9, 2022, and June 30, 2023, with a final follow-up on September 30, 2023.InterventionsEligible patients were randomly assigned to intravenous methylprednisolone (n = 839) at 2 mg/kg/d or placebo (n = 841) for 3 days adjunctive to endovascular thrombectomy. Main Outcomes and Measures The primary efficacy outcome was disability level at 90 days as measured by the overall distribution of the modified Rankin Scale scores (range, 0 [no symptoms] to 6 [death]). The primary safety outcomes included mortality at 90 days and the incidence of symptomatic intracranial hemorrhage within 48 hours. Results Among 1680 patients randomized (median age, 69 years; 727 female [43.3%]), 1673 (99.6%) completed the trial. The median 90-day modified Rankin Scale score was 3 (IQR, 1-5) in the methylprednisolone group vs 3 (IQR, 1-6) in the placebo group (adjusted generalized odds ratio for a lower level of disability, 1.10 [95% CI, 0.96-1.25]; P = .17). In the methylprednisolone group, there was a lower mortality rate (23.2% vs 28.5%; adjusted risk ratio, 0.84 [95% CI, 0.71-0.98]; P = .03) and a lower rate of symptomatic intracranial hemorrhage (8.6% vs 11.7%; adjusted risk ratio, 0.74 [95% CI, 0.55-0.99]; P = .04) compared with placebo. Conclusions and Relevance Among patients with acute ischemic stroke due to LVO undergoing endovascular thrombectomy, adjunctive methylprednisolone added to endovascular thrombectomy did not significantly improve the degree of overall disability.Trial RegistrationChiCTR.org.cn Identifier: ChiCTR210005172

Collaborative Dynamics Among Market Incumbents in the US Airline Industry, 1989–2010

In this study, we develop understanding of factors that shape the propensity of market incumbents to collaborate in response to the threat posed by new market entrants. We are particularly interested in instances when a market’s competitive structure becomes unsettled by new entrants who engage in nonconforming strategic tactics. In such situations, we propose two factors – strategic similarity among competitors and market-share instability – will systematically shape competitors’ collaborative response to new entrants. To test our theory, we use data on strategic tactics and collaborative dynamics in the US airline industry from 1989 to 2010. We demonstrate that greater strategic similarity among a market’s incumbents increases the likelihood of cooperation in response to the threat of a nonconforming new entrant, while greater market-share instability reduces cooperative response. Through this study, we extend existing understanding of the contextual circumstances under which established competitors recognize their mutual interests and band together

Glue or Gasoline? The Role of Interorganizational Relationships in the Spillover of Price Wars

This study investigates the role of self-enforced and third party-enforced interorganizational relationships (IORs) in influencing the spillover of price wars. Unlike previous research that emphasized economic factors (e.g., demand fluctuations and firm financial health) that precipitate price wars, this study underscores the relational aspect of price wars. Specifically, we argue that although self-enforced and third party-enforced relationships among competitors may both reduce the likelihood of price wars; once a war has started, third-party- enforced relationships will reduce the likelihood that a price war will spread into additional markets, while self-enforced relationships will increase the likelihood of such spillover. Using data from the United States (US) domestic airline industry from 1992 to 2010, our empirical evidence offers strong support for our predictions. By signifying the importance of IORs in the spillover of price wars, we hope to contribute to research on interorganizational relationships, as well as research on competition

Angiotensin-Converting Enzyme 2 Attenuates Bleomycin-Induced Lung Fibrosis in Mice

Background: Local renin-angiotensin system (RAS) activation has been shown to play an important role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). It has been reported that angiotensin-converting enzyme 2 (ACE2) could inhibit RAS-mediated epithelial injury and fibrogenesis and that ACE2 deficiency could aggravate acute and chronic lung injury. Through research, it could be deduced that ACE2 could protect against pulmonary fibrosis as a therapeutic target. Methods: Time-course analysis of the pathological characteristics of bleomycin-induced lung fibrosis was undertaken in a mouse model, and the effect of exogenous ACE2 on lung fibrosis was studied. Immunohistchemistry (IHC) staining and western blot (WB) testing for AGT and ACE2 were performed to evaluate the regulation of local RAS. TUNEL staining was used to observe epithelial apoptosis. Leukocyte common antigen (LCA) and pulmonary surfactant-associated protein A (SP-A) IHC staining and WB testing were performed to assess the inflammatory response and epithelial regeneration. Masson's staining and a hydroxyproline assay were performed to examine collagen deposition. IHC staining and WB testing for TGF-β1 and α-SMA were performed to investigate the regulation of pro-fibrotic cytokines and the activation of fibroblasts. Results: Exogenous ACE2 attenuated bleomycin-induced lung fibrosis by reversing the reduction of local ACE2 and by suppressing the elevation of AGT. ACE2 decreased the apoptosis index and LCA levels and ameliorated the dynamic change in SP-A level, thus protecting against epithelial injury. Reductions of TGF-β1 and α-SMA were also found in ACE2-treated mice, indicating the inhibition of fibrogenesis. Conclusion: ACE2 attenuated bleomycin-induced lung fibrosis as an anti-inflammatory anti-apoptotic and anti-fibrotic agent, and it might be a promising therapeutic target for IPF