Anisotropic superconducting properties of aligned MgB2 crystallites

Samples of aligned MgB2 crystallites have been prepared, allowing for the first time the direct identification of an upper critical field anisotropy Hc2^{ab}/Hc2^{c}= xi_{ab}/xi_{c} ~ 1.73; with xi_{o,ab} ~ 70 A, xi_{o,c} ~ 40 A, and a mass anisotropy ratio m_{ab}/m_{c} ~ 0.3. A ferromagnetic background signal was identified, possibly related to the raw materials purity.Comment: 4 pages, 4 figures; Revised version to appear in Phys. Rev. Let

Spin-dependent Fano resonance induced by conducting chiral helimagnet contained in a quasi-one-dimensional electron waveguide

Fano resonance appears for conduction through an electron waveguide containing donor impurities. In this work, we consider the thin-film conducting chiral helimagnet (CCH) as the donor impurity in a one-dimensional waveguide model. Due to the spin spiral coupling, interference between the direct and intersubband transmission channels gives rise to spin-dependent Fano resonance effect. The spin-dependent Fano resonance is sensitively dependent on the helicity of the spiral. By tuning the CCH potential well depth and the incident energy, this provides a potential way to detect the spin structure in the CCH.Comment: 14 pages, 6 figure

Scalar field perturbation on six-dimensional ultra-spinning black holes

We have studied the scalar field perturbations on six-dimensional ultra-spinning black holes. We have numerically calculated the quasinormal modes of rotating black holes. Our results suggest that such perturbations are stable.Comment: 8 pages, 6 figures; v2:typo corrected; v3:ref. corrected; v4:revise

The influence of institutional environment on venture capital development in emerging economies: the example of Nigeria

The aim of the study is to investigate the development of venture capital (VC) in an emerging economy lacking the fully-developed legal and financial institutions necessary to support private-equity financing. This study, undertaken in Nigeria, included extended interviews with venture capitalists (VCs), entrepreneurs who were able to secure VC funding and those who were not, a government minister and their key policy staff. The findings suggest that VCs require stable trusted institutional frameworks, regulations and tax regimes, alongside clear exit strategies. They also suggest that informal institution such as networking is important for VC development. These findings have major implications for VC policy and for the development of technology-based industrial start-ups. The paper contributes to the literature on the impact of institutions on VC development processes in emerging economies

Beyond the global financial crisis: challenges facing venture capitalists operating in an emerging economy such as Nigeria

Objectives: The study investigates the challenges faced by venture capitalists (VCs) when operating in an emerging market, as well as problems in dealing with the entrepreneurs themselves. This is to gain a deeper understanding of the environmental and governmental policy factors that are hindering the growth of the industry in Nigeria. Prior Work: In light of the recent global financial downturn where people are being made redundant, many could see it as an opportunity to start up their own business. However, the smooth operation of the finance escalator has proved difficult to achieve under recent financial conditions (North et al. 2013; Gill 2010; Mason et al 2010; NESTA 2009. Moreover, in an emerging economy, small business owners are more likely to secure funding for their new business venture from traditional sources rather than venture capital (VC) since they do not know much about it (Gupta and Sapienza, 2001). Jiang et al. (2014) argue that although the role of VCs is well documented in western developed economies, limited attention has been paid to it by SMEs in emerging markets. Approach: The data was collected using qualitative method involving interviews with 4 VCs who operate in Nigeria, 5 entrepreneurs who were not able to secure venture capital (VC) funding for their ventures and a government minister and a member of staff as key informants. Results: The results show that VCs who operate in Nigeria face challenges which are unique to an emerging economy. The findings suggest that people do not fully understand what VCs look for in a business, the benefits they bring to a business, how they work and the time it takes to get things done from a bureaucratic and legal perspective. Implications: The implication of the study is that the Nigerian government should take steps to improve the country’s VC industry by setting up of a VC fund for technology-based starts-ups. The government should also meet with the heads of the major financial houses in Nigeria in an effort to create a positive public relation campaign to highlight the benefits VCs bring to businesses. This will help significantly towards the development of the industry in Nigeria. Value: This study makes contribution to the growing body of literature on venture capital and the effect of global financial crisis. A better understanding of the decision making process of deal structuring will help VCs to make better decisions regarding investments and stages of funding. Understanding how VCs decide when and where to invest, might benefit entrepreneurs and SMEs with respect to attracting VC as well as increasing the likelihood of receiving higher levels of funding, because a higher level of financing gives them a bigger level of flexibility (Payne et al. (2009)

Extremal non-BPS black holes and entropy extremization

At the horizon, a static extremal black hole solution in N=2 supergravity in four dimensions is determined by a set of so-called attractor equations which, in the absence of higher-curvature interactions, can be derived as extremization conditions for the black hole potential or, equivalently, for the entropy function. We contrast both methods by explicitly solving the attractor equations for a one-modulus prepotential associated with the conifold. We find that near the conifold point, the non-supersymmetric solution has a substantially different behavior than the supersymmetric solution. We analyze the stability of the solutions and the extrema of the resulting entropy as a function of the modulus. For the non-BPS solution the region of attractivity and the maximum of the entropy do not coincide with the conifold point.Comment: 19 pages, 4 figures, AMS-LaTeX, reference adde