Direct observation of magnetization dynamics generated by nano-contact spin-torque vortex oscillators

Time-resolved scanning Kerr microscopy has been used to directly image the magnetization dynamics of nano-contact (NC) spin-torque vortex oscillators (STVOs) when phase-locked to an injected microwave (RF) current. The Kerr images reveal free layer magnetization dynamics that extend outside the NC footprint, where they cannot be detected electrically, but which are crucial to phase-lock STVOs that share common magnetic layers. For a single NC, dynamics were observed not only when the STVO frequency was fully locked to that of the RF current, but also for a partially locked state characterized by periodic changes in the core trajectory at the RF frequency. For a pair of NCs, images reveal the spatial character of dynamics that electrical measurements show to have enhanced amplitude and reduced linewidth. Insight gained from these images may improve understanding of the conditions required for mutual phase-locking of multiple STVOs, and hence enhanced microwave power emission.Comment: 10 pages, 3 figure

Observation of vortex dynamics in arrays of nanomagnets

Vortex dynamics within arrays of square ferromagnetic nanoelements have been studied by time-resolved scanningKerr microscopy (TRSKM),while x-ray photoemission electronmicroscopy has been used to investigate the equilibrium magnetic state of the arrays. An alternating field demagnetization process was found to initialize a distribution of equilibrium states within the individual elements of the array, including quasiuniform states and vortex states of different chirality and core polarization. Repeated initialization revealed some evidence of stochastic behavior during the formation of the equilibrium state. TRSKM with a spatial resolution of ∼300 nm was used to detect vortex gyration within arrays of square nanoelements of 250-nm lateral size. Two arrays were studied consisting of a 9 × 9 and 5 × 5 arrangement of nanoelements with 50- and 500-nm element edge-to-edge separation to encourage strong and negligible dipolar interactions, respectively. In the 5 × 5 element array, TRSKM images, acquired at a fixed phase of the driving microwave magnetic field, revealed differences in the gyrotropic phase within individual elements. While some phase variation is attributed to the dispersion in the size and shape of elements, the vortex chirality and core polarization are also shown to influence the phase. In the 9 × 9 array, strong magneto-optical response due to vortex gyration was observed across regions with length equal to either one or two elements. Micromagnetic simulations performed for 2 × 2 arrays of elements suggest that particular combinations of vortex chirality and polarization in neighboring elements are required to generate the observed magneto-optical contrast.Engineering and Physical Sciences Research Council (EPSRC

The price of rapid exit in venture capital-backed IPOs

This paper proposes an explanation for two empirical puzzles surrounding initial public offerings (IPOs). Firstly, it is well documented that IPO underpricing increases during “hot issue” periods. Secondly, venture capital (VC) backed IPOs are less underpriced than non-venture capital backed IPOs during normal periods of activity, but the reverse is true during hot issue periods: VC backed IPOs are more underpriced than non-VC backed ones. This paper shows that when IPOs are driven by the initial investor’s desire to exit from an existing investment in order to finance a new venture, both the value of the new venture and the value of the existing firm to be sold in the IPO drive the investor’s choice of price and fraction of shares sold in the IPO. When this is the case, the availability of attractive new ventures increases equilibrium underpricing, which is what we observe during hot issue periods. Moreover, I show that underpricing is affected by the severity of the moral hazard problem between an investor and the firm’s manager. In the presence of a moral hazard problem the degree of equilibrium underpricing is more sensitive to changes in the value of the new venture. This can explain why venture capitalists, who often finance firms with more severe moral hazard problems, underprice IPOs less in normal periods, but underprice more strongly during hot issue periods. Further empirical implications relating the fraction of shares sold and the degree of underpricing are presented

Emissões públicas de ações, volatilidade e insider information na Bovespa

O trabalho utiliza um estudo de evento para examinar os retornos de ações relacionados a emissões públicas por empresas brasileiras listadas na BOVESPA, realizadas entre 1992 e 2002, buscando determinar como o mercado reagiu antes, durante e depois da data do anúncio da emissão. Após utilizar a metodologia convencional de mensuração de retornos anormais por OLS, foram utilizados modelos ARCH e GARCH, que levam em consideração a heteroscedasticidade condicional da volatilidade dos retornos anormais, em mais de 70% da amostra, após a constatação da presença desses processos nos resíduos originais. Os resultados mostram que 1) há evidências de insider information antes da data do anúncio, (2) que ocorrem retornos anormais negativos na data do anúncio e (3) que, no período de um ano após as emissões, as ações das empresas que captaram recursos via underwriting tiveram retornos negativos após ajuste ao risco e ao mercado

Media Reporting and Business Cycles: Empirical Evidence based on News Data

Recent literature suggests that news shocks could be an important driver of economic cycles. In this article, we use a direct measure of news sentiment derived from media reports. This allows us to examine whether innovations in the reporting tone correlate with changes in the assessment and expectations of the business situation as reported by firms in the German manufacturing sector. We fi nd that innovations in news reporting affect business expectations, even when conditioning on the current business situation and industrial production. The dynamics of the empirical model con rm theoretical predictions that news innovations affect real variables such as production via changes in expectations. Looking at individual sectors within manufacturing, we fi nd that macroeconomic news is at least as important for business expectations as sector-spefici c news. This is consistent with the existence of information complementarities across sectors

Enhanced Neutrophil Extracellular Trap Formation in Acute Pancreatitis Contributes to Disease Severity and Is Reduced by Chloroquine

Background: Neutrophil extracellular traps (NETs) are generated when activated neutrophils, driven by PAD4, release their DNA, histones, HMGB1, and other intracellular granule components. NETs play a role in acute pancreatitis, worsening pancreatic inflammation, and promoting pancreatic duct obstruction. The autophagy inhibitor chloroquine (CQ) inhibits NET formation; therefore, we investigated the impact of CQ mediated NET inhibition in murine models of pancreatitis and human correlative studies. Methods: L-arginine and choline deficient ethionine supplemented (CDE) diet models of acute pancreatitis were studied in wild type and PAD4−/− mice, incapable of forming NETs. Isolated neutrophils were stimulated to induce NET formation and visualized with fluorescence microscopy. CQ treatment (0.5 mg/ml PO) was initiated after induction of pancreatitis. Biomarkers of NET formation, including cell-free DNA, citrullinated histone H3 (CitH3), and MPO-DNA conjugates were measured in murine serum and correlative human patient serum samples. Results: We first confirmed the role of NETs in the pathophysiology of acute pancreatitis by demonstrating that PAD4−/− mice had decreased pancreatitis severity and improved survival compared to wild-type controls. Furthermore, patients with severe acute pancreatitis had elevated levels of cell-free DNA and MPO-DNA conjugates, consistent with NET formation. Neutrophils from mice with pancreatitis were more prone to NET formation and CQ decreased this propensity to form NETs. CQ significantly reduced serum cell-free DNA and citrullinated histone H3 in murine models of pancreatitis, increasing survival in both models. Conclusions: Inhibition of NETs with CQ decreases the severity of acute pancreatitis and improves survival. Translating these findings into clinical trials of acute pancreatitis is warranted

Accommodating to English-medium instruction in teacher education in Finland

This study analyses teacher educators’ and student teachers’ perceptions of teaching and learning situations in an international English as a lingua franca (ELF) context in an English-medium instruction (EMI) teacher education programme in Finland. The analysis of semi-structured interviews revealed that the participants perceived a partial reversal of traditional teacher and student roles; students assisted voluntarily and teaching became reciprocal. Some teachers reflected on having used typical strategies in ELF context such as code-switching to further communication and engage students. However, teachers’ lack of fluency was sometimes considered causing frustration among students and affected negatively their feeling of being professional teacher educators. Nevertheless, by increasing more learner-led activities, ELF can positively affect teacher education pedagogy.Peer reviewe

Information diffusion in the U.S. real estate investment trust market

This study examines the information diffusion process in the U.S. Real Estate Investment Trust (REIT) market with a focus on the impacts of changing market environments, information supply, and information demand on the lead-lag effect. The results suggest that a significant lead-lag relationship exists between the lagged returns of big REITs and the current returns of small REITs. This relationship has slightly decreased along with policy and environment changes that occurred in the U.S. REIT market during the study period from 1986 to 2012, while still remaining significant in the most recent REIT market. The process of information diffusion is becoming unstable in recent years and the reverse lead-lag effect from small REITs to big REITs is observed especially when REIT market liquidity and return volatility are high. The lead-lag effect among REITs is driven largely by slow adjustment to negative information, which is magnified by a lack of information supply, especially as demand for such information increases. Finally, information flow from REITs with more media coverage to those with less media coverage becomes even more sluggish than the information flow from big REITs to small REITs