PORTFOLIO CONSTRUCTION IN TURBULENT MARKETS

We conducted the portfolio optimization on the selected benchmarks for nine asset classes with a time range starting from January 2007 to December 2016 in Canadian Currency, to prove whether the mean-variance approach by Markowitz (1952) combined with a covariance matrix blended from a quiet time and a turbulent time as introduced by Chow, G., Jacquier, E., Kritzman, M., and Lowry, K. (1999) is still valid with recent years’ data.As a result, the optimal portfolios with different covariance matrices blended from turbulent and quiet periods have shown sensitivity of optimal weights to both possibilities of occurrence for the turbulent and quiet periods, and different risk aversion to turbulent and quiet periods. The outlier-sample optimal portfolio is the most conservative one and provides a lowest expected return. Besides, the optimal weights of Cash are much higher due to the higher volatilities of ours benchmarks for US equity, emerging market equity, US bonds, high-yield bonds, and commodities

Consumer perceptions of co-branding alliances: Organizational dissimilarity signals and brand fit

This study explores how consumers evaluate co-branding alliances between dissimilar partner firms. Customers are well aware that different firms are behind a co-branded product and observe the partner firms’ characteristics. Drawing on signaling theory, we assert that consumers use organizational characteristics as signals in their assessment of brand fit and for their purchasing decisions. Some organizational signals are beyond the control of the co-branding partners or at least they cannot alter them on short notice. We use a quasi-experimental design and test how co-branding partner dissimilarity affects brand fit perception. The results show that co-branding partner dissimilarity in terms of firm size, industry scope, and country-of-origin image negatively affects brand fit perception. Firm age dissimilarity does not exert significant influence. Because brand fit generally fosters a benevolent consumer attitude towards a co-branding alliance, the findings suggest that high partner dissimilarity may reduce overall co-branding alliance performance

Angel investor's selection criteria: a comparative institutional perspective

Despite the important role of angel investors as critical financial providers for new ventures, little is known regarding how institutions make their investment decisions. While angels make decisions based on selection criteria during the first stage, they are also embedded within and affected by different institutional settings and as a result weight these criteria differently than other investors. We compare angel investors' selection criteria in China and Denmark using the comparative institutional perspective. We use a policy capturing approach and hierarchy linear modeling, revealing that since Chinese angels are embedded within relationship-based institutional settings they tend to reply more on strong ties such as family and friends in management team, as well as weighting risks less compared to Danish angels operating within more rule-based institutional contexts

The Cytosolic Domain of Fis1 Binds and Reversibly Clusters Lipid Vesicles

Every lipid membrane fission event involves the association of two apposing bilayers, mediated by proteins that can promote membrane curvature, fusion and fission. We tested the hypothesis that Fis1, a tail-anchored protein involved in mitochondrial and peroxisomal fission, promotes changes in membrane structure. We found that the cytosolic domain of Fis1 alone binds lipid vesicles, which is enhanced upon protonation and increasing concentrations of anionic phospholipids. Fluorescence and circular dichroism data indicate that the cytosolic domain undergoes a membrane-induced conformational change that buries two tryptophan side chains upon membrane binding. Light scattering and electron microscopy data show that membrane binding promotes lipid vesicle clustering. Remarkably, this vesicle clustering is reversible and vesicles largely retain their original shape and size. This raises the possibility that the Fis1 cytosolic domain might act in membrane fission by promoting a reversible membrane association, a necessary step in membrane fission

“Atomic-scale Origin of the Large Grain-boundary Resistance in Perovskite Li-ion-conducting

The solvent-based electrolytes used in conventional lithium-ion batteries can be unsafe and unstable for large-scale applications because of their combustible nature and narrow electrochemical window. Inorganic solid electrolytes, which are non-flammable and often possess much wider electrochemical windows, are being considered as the potential solution. However, the application of these electrolytes remains restricted due to their inherent, high grain-boundary (GB) resistance, which typically lowers the total ionic conductivity by several orders of magnitude. Identifying the ionic transport mechanism(s) at the GBs in solid electrolytes is critical for the revolutionary development of the next-generation of Li-ion batteries. In the present study, we reveal for the first time, the structural and chemical origins of the high GB resistivity in a (Li 3xLa 2/3-x)TiO 3 (LLTO) prototype solid electrolyte material. Unambiguous evidence acquired via sub-Å-resolution scanning transmission electron microscopy and electron energy loss spectroscopy analysis shows that the LLTO GBs exhibit a severe structural and chemical modification, which is significantly different from the bulk LLTO framework and results in a Ti-

Interfacial Stability of Li Metal–Solid Electrolyte Elucidated via in Situ Electron Microscopy

Despite their different chemistries, novel energy-storage systems, e.g., Li–air, Li–S, all-solid-state Li batteries, etc., face one critical challenge of forming a conductive and stable interface between Li metal and a solid electrolyte. An accurate understanding of the formation mechanism and the exact structure and chemistry of the rarely existing benign interfaces, such as the Li–cubic-Li_{7–3<i>x</i>}Al_<i>x</i>La₃Zr₂O₁₂ (c-LLZO) interface, is crucial for enabling the use of Li metal anodes. Due to spatial confinement and structural and chemical complications, current investigations are largely limited to theoretical calculations. Here, through an in situ formation of Li–c-LLZO interfaces inside an aberration-corrected scanning transmission electron microscope, we successfully reveal the interfacial chemical and structural progression. Upon contact with Li metal, the LLZO surface is reduced, which is accompanied by the simultaneous implantation of Li⁺, resulting in a tetragonal-like LLZO interphase that stabilizes at an extremely small thickness of around five unit cells. This interphase effectively prevented further interfacial reactions without compromising the ionic conductivity. Although the cubic-to-tetragonal transition is typically undesired during LLZO synthesis, the similar structural change was found to be the likely key to the observed benign interface. These insights provide a new perspective for designing Li–solid electrolyte interfaces that can enable the use of Li metal anodes in next-generation batteries

Formation of the Conducting Filament in TaO_<i>x</i>‑Resistive Switching Devices by Thermal-Gradient-Induced Cation Accumulation

The distribution of tantalum and oxygen ions in electroformed and/or switched TaO_<i>x</i>-based resistive switching devices has been assessed by high-angle annular dark-field microscopy, X-ray energy-dispersive spectroscopy, and electron energy-loss spectroscopy. The experiments have been performed in the plan-view geometry on the cross-bar devices producing elemental distribution maps in the direction perpendicular to the electric field. The maps revealed an accumulation of +20% Ta in the inner part of the filament with a 3.5% Ta-depleted ring around it. The diameter of the entire structure was approximately 100 nm. The distribution of oxygen was uniform with changes, if any, below the detection limit of 5%. We interpret the elemental segregation as due to diffusion driven by the temperature gradient, which in turn is induced by the spontaneous current constriction associated with the negative differential resistance-type <i>I</i>–<i>V</i> characteristics of the as-fabricated metal/oxide/metal structures. A finite-element model was used to evaluate the distribution of temperature in the devices and correlated with the elemental maps. In addition, a fine-scale (∼5 nm) intensity contrast was observed within the filament and interpreted as due phase separation of the functional oxide in the two-phase composition region. Understanding the temperature-gradient-induced phenomena is central to the engineering of oxide memory cells