Brownian motion in a non-homogeneous force field and photonic force microscope

The Photonic Force Microscope (PFM) is an opto-mechanical technique based on an optical trap that can be assumed to probe forces in microscopic systems. This technique has been used to measure forces in the range of pico- and femto-Newton, assessing the mechanical properties of biomolecules as well as of other microscopic systems. For a correct use of the PFM, the force field to measure has to be invariable (homogeneous) on the scale of the Brownian motion of the trapped probe. This condition implicates that the force field must be conservative, excluding the possibility of a rotational component. However, there are cases where these assumptions are not fulfilled Here, we show how to improve the PFM technique in order to be able to deal with these cases. We introduce the theory of this enhanced PFM and we propose a concrete analysis workflow to reconstruct the force field from the experimental time-series of the probe position. Furthermore, we experimentally verify some particularly important cases, namely the case of a conservative or rotational force-field

The Augmented SOLOW Model And The OECD Sample

In their influential work on the augmented Solow model, Mankiw, Romer and Weil (1992) showed that cross-section evidence was reasonably consistent with the Solow growth model augmented to include human capital for a wide range of countries.  However, for the sample of OECD countries, they found that the model had low explanatory power and underestimated the output elasticity of physical capital. We revisit their seminal work using data from the recently released version 6.1 of the Penn World Table. We find that the ability of the augmented Solow model to explain the cross-country variation in income per capita in the OECD sample improves significantly. Our results highlight the importance of taking into account changes that take place over time in the collection and measurement of national accounts data in estimating and testing the augmented Solow model

The Mixture Of Distribution Hypothesis And The Russian Stock Market

According to the mixture of distributions hypothesis (MDH), a serially correlated mixture of variables measuring the rate at which information arrives to the market explains the GARCH effects in stock returns. While reasonable amount of empirical evidence supports this hypothesis for developed, highly liquid stock markets in industrial countries, the current literature does not provide much findings for stock markets in countries that have recently experienced the transition from economic planning to capitalism. Hence, the purpose of this paper is to provide a first piece of evidence for one of the newly created stock market, the Russian stock market. Examination of the relationship between risk, returns, volatility and volume existing in the Russian stock market provides evidence in support of the MDH and suggests that even in emerging and turbulent markets risk and returns are jointly integrated to the flow of information arriving to the market

Imaging fractional incompressible stripes in integer quantum Hall systems

Transport experiments provide conflicting evidence on the possible existence of fractional order within integer quantum Hall systems. In fact integer edge states sometimes behave as monolithic objects with no inner structure, while other experiments clearly highlight the role of fractional substructures. Recently developed low-temperature scanning probe techniques offer today an opportunity for a deeper-than-ever investigation of spatial features of such edge systems. Here we use scanning gate microscopy and demonstrate that fractional features were unambiguously observed in every integer quantum Hall constriction studied. We present also an experimental estimate of the width of the fractional incompressible stripes corresponding to filling factors 1/3, 2/5, 3/5, and 2/3. Our results compare well with predictions of the edge-reconstruction theory

GC3 of genes can be used as a proxy for isochore base composition: A reply to Elhaik et al.

In an article published in these pages, Elhaik et al. (Elhaik E, Landan G, Graur D. 2009. Can GC content at third-codon positions be used as a proxy for isochore composition? Mol Biol Evol. 26:1829-1833) asked if GC3, the GC level of the third-codon positions in protein-coding genes, can be used as a 'proxy' to estimate the GC level of the surrounding isochore. We use available data to directly answer this simple question in the affirmative and show how the use of indirect methods can lead to apparently conflicting conclusions. The answer reasserts that in human and other vertebrates, genes have a strong tendency to reside in compositionally corresponding isochores, which has far-reaching implications for genome structure and evolution. © 2010 The Author

Maximally multipartite entangled states

We introduce the notion of maximally multipartite entangled states of n qubits as a generalization of the bipartite case. These pure states have a bipartite entanglement that does not depend on the bipartition and is maximal for all possible bipartitions. They are solutions of a minimization problem. Examples for small n are investigated, both analytically and numerically.Comment: 5 pages, 1 figure, final verso

Clustering in Complex Directed Networks

Many empirical networks display an inherent tendency to cluster, i.e. to form circles of connected nodes. This feature is typically measured by the clustering coefficient (CC). The CC, originally introduced for binary, undirected graphs, has been recently generalized to weighted, undirected networks. Here we extend the CC to the case of (binary and weighted) directed networks and we compute its expected value for random graphs. We distinguish between CCs that count all directed triangles in the graph (independently of the direction of their edges) and CCs that only consider particular types of directed triangles (e.g., cycles). The main concepts are illustrated by employing empirical data on world-trade flows

Extended endoscopic endonasal transsphenoidal approach to the suprasellar area: Anatomic considerations - Part I

INTRODUCTION: Interest in using the extended endonasal transsphenoidal approach for management of suprasellar lesions, with either a microscopic or endoscopic technique, has increased in recent years. The most relevant benefit is that this median approach permits the exposure and removal of suprasellar lesions without the need for brain retraction. MATERIALS AND METHODS: Fifteen human cadaver heads were dissected to evaluate the surgical key steps and the advantages and limitations of the extended endoscopic endonasal transplanum sphenoidale approach. We compared this with the transcranial microsurgical view of the suprasellar area as explored using the bilateral subfrontal microsurgical approach, and with the anatomy of the same region as obtained through the endoscopic endonasal route. RESULTS: Some anatomic conditions can prevent or hinder use of the extended endonasal approach. These include a low level of sphenoid sinus pneumatization, a small sella size with small distance between the internal carotid arteries, a wide intercavernous sinus, and a thick tuberculum sellae. Compared with the subfrontal transcranial approach, the endoscopic endonasal approach offers advantages to visualizing the subchiasmatic, retrosellar, and third ventricle areas. CONCLUSION: The endoscopic endonasal transplanum sphenoidale technique is a straight, median approach to the midline areas around the sella that provides a multiangled, close-up view of all relevant neurovascular structures. Although a lack of adequate instrumentation makes it impossible to manage all structures that are visible with the endoscope, in selected cases, the extended endoscopic endonasal approach can be considered part of the armamentarium for surgical treatment of the suprasellar area