A stochastical model for periodic domain structuring in ferroelectric crystals

A stochastical description is applied in order to understand how ferroelectric structures can be formed. The predictions are compared with experimental data of the so-called electrical fixing: Domains are patterned in photorefractive lithium niobate crystals by the combination of light-induced space-charge fields with externally applied electrical fields. In terms of our stochastical model the probability for domain nucleation is modulated according to the sum of external and internal fields. The model describes the shape of the domain pattern as well as the effective degree of modulation

The Making of Cloud Applications An Empirical Study on Software Development for the Cloud

Cloud computing is gaining more and more traction as a deployment and provisioning model for software. While a large body of research already covers how to optimally operate a cloud system, we still lack insights into how professional software engineers actually use clouds, and how the cloud impacts development practices. This paper reports on the first systematic study on how software developers build applications in the cloud. We conducted a mixed-method study, consisting of qualitative interviews of 25 professional developers and a quantitative survey with 294 responses. Our results show that adopting the cloud has a profound impact throughout the software development process, as well as on how developers utilize tools and data in their daily work. Among other things, we found that (1) developers need better means to anticipate runtime problems and rigorously define metrics for improved fault localization and (2) the cloud offers an abundance of operational data, however, developers still often rely on their experience and intuition rather than utilizing metrics. From our findings, we extracted a set of guidelines for cloud development and identified challenges for researchers and tool vendors

Trapping of dielectric particles with light-induced space-charge fields

Light-induced space-charge fields in lithium niobate crystals are used to trap and manipulate dielectric particles on the surface of such crystals. Without any external voltage source, strong field gradients are present in the proximity of the crystal surface. These are used to trap particles with diameters in the range between 100 nm and some tens of micrometers

Poling effect on distribution of quenched random fields in a uniaxial relaxor ferroelectric

The frequency dependence of the dielectric permitivity's maximum has been studied for poled and unpoled doped relaxor strontium barium niobate $Sr_{0.61}Ba_{0.39}Nb_{2}O_{6}:Cr^{3+}$ (SBN-61:Cr). In both cases the maximum found is broad and the frequency dispersion is strong. The present view of random fields compensation in the unpoled sample is not suitable for explaining this experimental result. We propose a new mechanism where the dispersion of quenched random electric fields, affecting the nanodomains, is minimized after poling. We test our proposal by numerical simulations on a random field Ising model. Results obtained are in agreement with the polarization's measurements presented by Granzow et al. [Phys. Rev. Lett {\bf 92}, 065701 (2004)].Comment: 7 pages, 4 figure

Role of cerium in lithium niobate for holographic recording

Cerium-doped lithium niobate crystals are tested for holographic recording. A photochromic effect is observed in crystals doped with cerium and manganese. But two-center recording in the sample is not as effective as in iron and manganese doubly doped crystals. Photocurrent measurements in cerium and iron singly doped crystals indicate that the photovoltaic constant in the cerium-doped crystal is only one third of that of the iron-doped one. This is the main reason accounting for the low sensitivity of cerium-doped lithium niobate crystals. However, in the diffusion dominated case, i.e., for reflection geometry, cerium-doped lithium niobate may give a strong effect

Connections between the stability of a Poincare map and boundedness of certain associate sequences

Let $m\ge 1$ and $N\ge 2$ be two natural numbers and let ${\mathcal{U}}=\{U(p, q)\}_{p\ge q\ge 0}$ be the $N$-periodic discrete evolution family of $m\times m$ matrices, having complex scalars as entries, generated by ${\mathcal{L}}(\mathbb{C}^m)$-valued, $N$-periodic sequence of $m\times m$ matrices $(A_n).$ We prove that the solution of the following discrete problem $$y_{n+1}=A_ny_n+e^{i\mu n}b,\quad n\in\mathbb{Z}_+,\quad y_0=0$$ is bounded for each $\mu\in\mathbb{R}$ and each $m$-vector $b$ if the Poincare map $U(N, 0)$ is stable. The converse statement is also true if we add a new assumption to the boundedness condition. This new assumption refers to the invertibility for each $\mu\in\mathbb{R}$ of the matrix $V_{\mu}:=\sum\nolimits_{\nu=1}^NU(N, \nu)e^{i\mu \nu}.$ By an example it is shown that the assumption on invertibility cannot be removed. Finally, a strong variant of Barbashin's type theorem is proved

Towards a Framework Convention on Global Health

A global health treaty, a Framework Convention on Global Health (FCGH)–grounded in the right to health, with the central goal of reducing immense domestic and global health inequities–could serve as a robust global governance instrument to underpin the United Nations post-2015 Millennium Development Goals (MDGs). It would ensure for all people the three essential conditions for a healthy life–public health, health care, and the positive social determinants of health–while advancing good governance, responding to drivers of health disadvantages for marginalized populations, elevating health in other legal regimes, and enhancing people\u27s ability to claim their rights. The legally binding nature of the FCGH would enhance accountability and compliance through rigorous monitoring and reporting, domestic human rights litigation, and international incentives. It would overcome the collection action problem of global health financing through a health financing framework with clear domestic and international obligations. Stakeholders have made thoughtful critiques of the FCGH, such as the opportunities costs of advocacy, the time and expense of treaty negotiations, and reporting burdens. Nevertheless, these costs could be turned into opportunities through civil society participation in negotiations, by taking advantage of extensive reporting and monitoring requirements to expand accountability around and strengthen strategies to respond to health inequities, and through non-binding frameworks on the way towards the treaty. The greatest challenge in achieving an FCGH is the political obstacles it will face. Social justice movements united behind an FCGH, to secure the treaty and to ensure its implementation, are vital to the success of an FCGH–and the right to health. With its aim of securing this right, the FCGH could unite disparate health-related movements, all of which should contribute to developing the treaty and taking ownership of its realization

Unpacking ‘women’s health’ in the context of PPPs: a return to instrumentalism in development policy and practice?

There has been a significant increase in funding for health programmes in development over the last two decades, partly due to the formation of public–private partnerships. This article examines the impact of public–private partnerships from the perspective of women’s health, asks whether the current culture of funding has led to an increased instrumentalism in women’s health programming and what effects this has on how women’s health is addressed at the level of practice. The article is based on research carried out with UK-based non-governmental organisations (NGOs), and its conclusions raise further challenges for improving women’s health policies and programmes in development

The prognostic value of troponin release after adult cardiac surgery — a meta-analysis

To assess the accuracy of increased troponin (Tn) concentrations for the prediction of mid-term (≥12 months) mortality after coronary artery bypass graft (CABG) and valve surgery, we performed a systematic review identifying all studies reporting on the association between postoperative troponin release and mortality after cardiac surgery. Studies were identified through 30 April 2008 by electronic searches of the MEDLINE, EMBASE and BIOSIS databases. Two reviewers independently selected studies, assessed methodological quality and extracted the data. We primarily considered mid-term (≥12 months) and secondarily short-term (≤30 days) all-cause mortality. A bivariate random-effects model was used to study determinants and to pool measures of prognostic accuracy of Tn. Seventeen studies fulfilled the inclusion criteria with a total of 237 mid-term deaths in 5189 patients and 296 short-term deaths in 9703 patients. The diagnostic odds ratio of increased Tn concentrations was 5.46 (95% confidence interval (CI) 2.0-14.6) for mid-term mortality and 6.57 (95% CI 4.3-10.1) for short-term mortality after adult cardiac surgery. Alternatively expressed, for troponin elevation, the sensitivity was 0.45 (0.26-0.67) and the specificity 0.87 (0.73-0.90) to predict mid-term mortality. The sensitivity was 0.59 (0.48-0.69) and the specificity 0.82 (0.72-0.89) for short-term mortality. Between-study variability was high. In conclusion, this meta-analysis provides evidence for an association between postoperative Tn release with mid- and short-term all-cause mortality after adult cardiac surgery. However, differences in populations, timing of Tn testing, Tn subunit and Tn assays make definitive conclusions about effect size and cut-off values difficul