Metastable Flux Configurations and de Sitter Spaces

We derive stability conditions for the critical points of the no-scale scalar potential governing the dynamics of the complex structure moduli and the axio-dilaton in compactifications of type IIB string theory on Calabi-Yau three-folds. We discuss a concrete example of a T^6 orientifold. We then consider the four-dimensional theory obtained from compactifications of type IIB string theory on non-geometric backgrounds which are mirror to rigid Calabi-Yau manifolds and show that the complex structure moduli fields can be stabilized in terms of H_{RR} only, i.e. with no need of orientifold projection. The stabilization of all the fields at weak coupling, including the axio-dilaton, may require to break supersymmetry in the presence of H_{NS} flux or corrections to the scalar potential.Comment: 24 page

Experimental techniques for ductile damage characterisation

Ductile damage in metallic materials is caused by the nucleation, growth and coalesce of voids and micro-cracks in the metal matrix when it is subjected to plastic strain. A considerable number of models have been proposed to represent ductile failure focusing on the ultimate failure conditions; however, only some of them study in detail the whole damage accumulation process. The aim of this work is to review experimental techniques developed by various authors to measure the accumulation of ductile damage under tensile loads. The measurement methods reviewed include: stiffness degradation, indentation, microstructure analysis, ultrasonic waves propagation, X-ray tomography and electrical potential drop. Stiffness degradation and indentation techniques have been tested on stainless steel 304L hourglass-shaped samples. A special interest is placed in the Continuum Damage Mechanics approach (CDM) as its equations incorporate macroscopic parameters that can represent directly the damage accumulation measured in the experiments. The other main objective lies in identifying the strengths and weaknesses of each technique for the assessment of materials subjected to different strain-rate and temperature conditions

Learning or Leaning: Persistent and Transitory Spillovers from FDI

Using firm-level data for Jordan, we estimate the extent to which growth spillovers from foreign direct investment (FDI) to local firms stem from persistent learning externalities (i.e., they endure even after foreign investment leaves as knowledge has been transferred to local firms) or from transitory effects (e.g., demand increases which evaporate following disinvestment). We find that they have a significant transitory nature, with employment and capital growth declining when FDI falls, particularly in downstream industries supplied by locals. This suggests that if FDI-attracting policies are intended to promote sustainable growth, it may be more effective to attract and retain FDI via long-term structural policies, for instance, through low corporate tax rates rather than temporary tax holidays or through policies that strengthen the domestic absorptive capacity and linkages between foreign and local firms. It also suggests that FDI-led growth can increase a country's vulnerability to adverse global shocks in that the productivity gains of domestic firms will be partly reversed with the disinvestment of multinational firms

Structure-mechanics relationships of collagen fibrils in the Osteogenesis Imperfecta Mouse model

The collagen molecule, which is the building block of collagen fibrils, is a triple helix of two α1(I) chains and one α2(I) chain. However, in the severe mouse model of osteogenesis imperfecta (OIM), deletion of the COL1A2 gene results in the substitution of the α2(I) chain by one α1(I) chain. As this substitution severely impairs the structure and mechanics of collagen-rich tissues at the tissue and organ level, the main aim of this study was to investigate how the structure and mechanics are altered in OIM collagen fibrils. Comparing results from atomic force microscopy imaging and cantilever-based nanoindentation on collagen fibrils from OIM and wild-type (WT) animals, we found a 33% lower indentation modulus in OIM when air-dried (bound water present) and an almost fivefold higher indentation modulus in OIM collagen fibrils when fully hydrated (bound and unbound water present) in phosphate-buffered saline solution (PBS) compared with WT collagen fibrils. These mechanical changes were accompanied by an impaired swelling upon hydration within PBS. Our experimental and atomistic simulation results show how the structure and mechanics are altered at the individual collagen fibril level as a result of collagen gene mutation in OIM. We envisage that the combination of experimental and modelling approaches could allow mechanical phenotyping at the collagen fibril level of virtually any alteration of collagen structure or chemistry.United States. Dept. of Defense. Presidential Early Career Award for Scientists and EngineersNational Science Foundation (U.S.) (CAREER Award

A comparison of the optical properties of InGaN/GaN multiple quantum well structures grown with and without Si-doped InGaN prelayers

In this paper, we report on a detailed spectroscopic study of the optical properties of InGaN/GaN multiple quantum well structures, both with and without a Si-doped InGaN prelayer. In photoluminescence and photoluminescence excitation spectroscopy, a 2nd emission band, occurring at a higher energy, was identified in the spectrum of the multiple quantum well structure containing the InGaN prelayer, originating from the first quantum well in the stack. Band structure calculations revealed that a reduction in the resultant electric field occurred in the quantum well immediately adjacent to the InGaN prelayer, therefore leading to a reduction in the strength of the quantum confined Stark effect in this quantum well. The partial suppression of the quantum confined Stark effect in this quantum well led to a modified (higher) emission energy and increased radiative recombination rate. Therefore, we ascribed the origin of the high energy emission band to recombination from the 1st quantum well in the structure. Study of the temperature dependent recombination dynamics of both samples showed that the decay time measured across the spectrum was strongly influenced by the 1st quantum well in the stack (in the sample containing the prelayer) leading to a shorter average room temperature lifetime in this sample. The room temperature internal quantum efficiency of the prelayer containing sample was found to be higher than the reference sample (36% compared to 25%) which was thus attributed to the faster radiative recombination rate of the 1st quantum well providing a recombination pathway that is more competitive with non-radiative recombination processes.This work was carried out with the financial support of the United Kingdom Engineering and Physical Sciences Research Council under Grant Nos. EP/I012591/1 and EP/ H011676/1.This is the final version of the article. It first appeared from AIP Publishing via http://dx.doi.org/10.1063/1.494132

Found: High Surface Brightness Compact Galaxies

We are using the 2dF spectrograph to make a survey of all objects (`stars' and `galaxies') in a 12 sq.deg region towards the Fornax cluster. We have discovered a population of compact emission-line galaxies unresolved on photographic sky survey plates and therefore missing in most galaxy surveys based on such material. These galaxies are as luminous as normal field galaxies. Using H-alpha to estimate star formation they contribute at least an additional 5 per cent to the local star formation rate.Comment: To appear in "The Low Surface Brightness Universe", IAU Coll 171, eds. J.I. Davies et al., A.S.P. Conference Series. 3 pages, LaTex, 1 encapsulated ps-figure, requires paspconf.st

Crystallisation of Aspirin via Simulated Pulmonary Surfactant Monolayers and Lung-Specific Additives

Pain is a prevalent condition that can have a serious impact upon the socioeconomic function of a population. Numerous methods exist to administer analgesic medication (e.g. aspirin) to the body however inherent drawbacks limit patient acceptability. The inhaled route offers promise to facilitate the administration of medication to the body. Here, we consider the crystallisation behaviour of aspirin, our model therapeutic agent, when in contact with material of relevance to the lung. Thus, our approach aims to better understand the interaction between drug substances and the respiratory tract. Langmuir monolayers composed of a mixed surfactant system were supported on an aqueous subphase containing aspirin (7.5mg/ml). The surfactant film was compressed to either 5mN/m (i.e. inhalation end point) or 50mN/m (i.e. exhalation end point), whilst located within a humid environment for 16 hours. Standard cooling crystallisation procedures were employed to produce control samples. Antisolvent crystallisation in the presence or absence of lung-specific additives was conducted. All samples were analysed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). Drug-surfactant interactions were confirmed via condensed Langmuir isotherms. SEM analysis revealed plate-like morphology. The crystallisation route dictated both the crystal habit and particle size distribution. Dominant reflections were the (100) and (200) aspects. The main modes of interaction were hydrogen bonding, hydrophobic associations and van der Waals forces. Here, we have demonstrated the potential of antisolvent crystallisation with lung-specific additives to achieve control over drug crystal morphology. The approach taken can be applied in respirable formulation engineering

Nilpotent normal form for divergence-free vector fields and volume-preserving maps

We study the normal forms for incompressible flows and maps in the neighborhood of an equilibrium or fixed point with a triple eigenvalue. We prove that when a divergence free vector field in $\mathbb{R}^3$ has nilpotent linearization with maximal Jordan block then, to arbitrary degree, coordinates can be chosen so that the nonlinear terms occur as a single function of two variables in the third component. The analogue for volume-preserving diffeomorphisms gives an optimal normal form in which the truncation of the normal form at any degree gives an exactly volume-preserving map whose inverse is also polynomial inverse with the same degree.Comment: laTeX, 20 pages, 1 figur

Pharmacy Apps: a new frontier on the digital landscape?

BACKGROUND: Over the course of recent years smartphone and tablet technology has evolved rapidly. Similarly, the sphere of healthcare is constantly developing and striving to embrace the newest forms of technology in order to optimise function. Many opportunities for mobile applications (i.e. 'apps') pertinent to the healthcare sector are now emerging. OBJECTIVE: This study will consider whether registered pharmacists within the United Kingdom (UK) believe it appropriate to use mobile apps during the provision of healthcare within the community setting. METHODS: Further to Liverpool John Moores University (LJMU) ethical approval, the 30 item questionnaire was distributed to UK registered pharmacists (n=600) practising within inner city Manchester, Liverpool and Newcastle. The questions were formatted as multiple choice, Likert scales or the open answer type. On questionnaire completion and return, data were analysed using simple frequencies, cross tabulations and non-parametric techniques in the Statistical Package for the Social Sciences (SPSS) (v18). RESULTS: The majority of respondents (78.4% of 211 participants) confirmed that they were confident when using mobile apps on their technology platform. In general, mobile apps were perceived to be useful in facilitating patient consultations (55%) and supporting healthcare education (80%). The main barrier for mobile app use within the workplace was company policy, deemed significant in the case of regional / national chain pharmacies (p<0.001). Pharmacists alluded to the fact that whilst mobile apps demonstrate potential in modern day practise, they will have a greater impact in the future (p<0.001). CONCLUSION: The data indicate that although pharmacists are supportive of mobile apps in healthcare, a number of factors (i.e. risk, company policy and lack of regulation) may preclude their use in modern day pharmacy practise. Clearly, limitations of the technology must be addressed in order to maximise uptake within healthcare systems. Pharmacists suggest that as the younger generation ages, mobile apps will become a more accepted method by which to manage healthcare in the wider population