The transform likelihood ratio method for rare event simulation with heavy tails

We present a novel method, called the transform likelihood ratio (TLR) method, for estimation of rare event probabilities with heavy-tailed distributions. Via a simple transformation ( change of variables) technique the TLR method reduces the original rare event probability estimation with heavy tail distributions to an equivalent one with light tail distributions. Once this transformation has been established we estimate the rare event probability via importance sampling, using the classical exponential change of measure or the standard likelihood ratio change of measure. In the latter case the importance sampling distribution is chosen from the same parametric family as the transformed distribution. We estimate the optimal parameter vector of the importance sampling distribution using the cross-entropy method. We prove the polynomial complexity of the TLR method for certain heavy-tailed models and demonstrate numerically its high efficiency for various heavy-tailed models previously thought to be intractable. We also show that the TLR method can be viewed as a universal tool in the sense that not only it provides a unified view for heavy-tailed simulation but also can be efficiently used in simulation with light-tailed distributions. We present extensive simulation results which support the efficiency of the TLR method.

Method for the generation and cultivation of functional three-dimensional mammary constructs without exogenous extracellular matrix

During puberty, pregnancy, lactation and postlactation, breast tissue undergoes extensive remodelling and the disruption of these events can lead to cancer. In vitro studies of mammary tissue and its malignant transformation regularly employ mammary epithelial cells cultivated on matrigel or floating collagen rafts. In these cultures, mammary epithelial cells assemble into three-dimensional structures resembling in vivo acini. We present a novel technique for generating functional mammary constructs without the use of matrix substitutes.

Non-linear principal components analysis: an alternative method for finding patterns in environmental data

The main purpose of this article is to gain an insight into the relationships between variables describing the environmental conditions of the Far Northern section of the Great Barrier Reef, Australia, Several of the variables describing these conditions had different measurement levels and often they had non-linear relationships. Using non-linear principal component analysis, it was possible to acquire an insight into these relationships. Furthermore. three geographical areas with unique environmental characteristics could be identified. Copyright (c) 2005 John Wiley & Sons, Ltd.

The development of a modified dissolution method suitable for investigating powder mixtures

A novel dissolution method was developed, suitable for powder mixtures, based on the USP basket apparatus. The baskets were modified such that the powder mixtures were retained within the baskets and not dispersed, a potential difficulty that may arise when using conventional USP basket and paddle apparatus. The advantages of this method were that the components of the mixtures were maintained in close proximity, maximizing any drug:excipient interaction and leading to more linear dissolution profiles. Two weakly acidic model drugs, ibuprofen and acetaminophen, and a selection of pharmaceutical excipients, including potential dissolution-enhancing alkalizing agents, were chosen for investigation. Dissolution profiles were obtained for simple physical mixtures. The f1 fit factor values, calculated using pure drug as the reference material, demonstrated a trend in line with expectations, with several dissolution enhancers apparent for both drugs. Also, the dissolution rates were linear over substantial parts of the profiles. For both drugs, a rank order comparison between the f1 fit factor and calculated dissolution rate, obtained from the linear section of the dissolution profile, demonstrated a correlation using a significance level of P=0.05. The method was proven to be suitable for discriminating between the effects of excipients on the dissolution of the model drugs. The method design produced dissolution profiles where the dissolution rate was linear for a substantial time, allowing determination of the dissolution rate without mathematical transformation of the data. This method may be suitable as a preliminary excipient-screening tool in the drug formulation development process.

An integral equation method for a mixed initial boundary value problem for unsteady Stokes system in a doubly-connected domain

We present a novel numerical method for a mixed initial boundary value problem for the unsteady Stokes system in a planar doubly-connected domain. Using a Laguerre transformation the unsteady problem is reduced to a system of boundary value problems for the Stokes resolvent equations. Employing a modied potential approach we obtain a system of boundary integral equations with various singularities and we use a trigonometric quadrature method for their numerical solution. Numerical examples are presented showing that accurate approximations can be obtained with low computational cost.

Segmentation of a Speech Signal with Application of Fast Wavelet Transformation

The article describes the method of preliminary segmentation of a speech signal with wavelet transformation use, consisting of two stages. At the first stage there is an allocation of sibilants and pauses, at the second – the further segmentation of the rest signal parts.

Identifying DNA-binding proteins by combining support vector machine and PSSM distance transformation

Background: DNA-binding proteins play a pivotal role in various intra- and extra-cellular activities ranging from DNA replication to gene expression control. Identification of DNA-binding proteins is one of the major challenges in the field of genome annotation. There have been several computational methods proposed in the literature to deal with the DNA-binding protein identification. However, most of them can't provide an invaluable knowledge base for our understanding of DNA-protein interactions. Results: We firstly presented a new protein sequence encoding method called PSSM Distance Transformation, and then constructed a DNA-binding protein identification method (SVM-PSSM-DT) by combining PSSM Distance Transformation with support vector machine (SVM). First, the PSSM profiles are generated by using the PSI-BLAST program to search the non-redundant (NR) database. Next, the PSSM profiles are transformed into uniform numeric representations appropriately by distance transformation scheme. Lastly, the resulting uniform numeric representations are inputted into a SVM classifier for prediction. Thus whether a sequence can bind to DNA or not can be determined. In benchmark test on 525 DNA-binding and 550 non DNA-binding proteins using jackknife validation, the present model achieved an ACC of 79.96%, MCC of 0.622 and AUC of 86.50%. This performance is considerably better than most of the existing state-of-the-art predictive methods. When tested on a recently constructed independent dataset PDB186, SVM-PSSM-DT also achieved the best performance with ACC of 80.00%, MCC of 0.647 and AUC of 87.40%, and outperformed some existing state-of-the-art methods. Conclusions: The experiment results demonstrate that PSSM Distance Transformation is an available protein sequence encoding method and SVM-PSSM-DT is a useful tool for identifying the DNA-binding proteins. A user-friendly web-server of SVM-PSSM-DT was constructed, which is freely accessible to the public at the web-site on http://bioinformatics.hitsz.edu.cn/PSSM-DT/.

Mechanistic study of arsenic uptake, transformation and tolerance in arsenic hyperaccumulator Pteris vittata

Pteris vittata, the first reported arsenic hyperaccumulating plant, is potentially used in phytoremediation of arsenic, as it can accumulate up to 2.3% of arsenic in its fronds. In this study, the mechanisms of arsenic tolerance, uptake and transformation were studied in the plant. Arsenic species were analyzed by HPLC-AFS. Results showed that arsenic was mainly accumulated in leaflets, and inorganic arsenate and arsenite were only species in P. vittata. Arsenite was the predominant species in leaflets, whereas arsenate was the predominant species in roots. Arsenic induced the synthesis of thiol containing compounds in P. vittata. As-induced thiol was purified by a novel method: covalent chromatography following preparative HPLC. The purified thiol was characterized as a phytochelatin with two units (PC2). ^ In P. vittata, enhanced tolerance likely results from unusual intracellular detoxification mechanisms. Although PC-dependent sequestration of arsenic into vacuoles is essential for nonhyperaccumulators, this sequestration is not the major arsenic tolerance mechanisms in this arsenic hyperaccumulator. PC-independent sequestration of arsenic is likely the major arsenic tolerance mechanism. PC-dependent arsenic detoxification is probably a supplement to this major mechanism. ^ Interactions between arsenic and phosphate were studied. Under hydroponic condition, arsenic supply decreased the concentrations of phosphate in roots. In soil, arsenic increased the concentrations of phosphate in roots. Arsenic concentrations in rachises and leaflets were not affected by arsenic supply in either hydroponic or soil system. Phosphate decreased arsenic accumulation in roots, rachises and leaflets in the hydroponic system. ^ The uptake kinetics of arsenate, arsenite, monomethyl arsinic acid (MMA), dimethyl arsonic acid, and phosphate were studied in P. vittata. Phosphate uptake systems in Pteris vittata cannot distinguish phosphate and As(V), resulting in As hyperaccumulation. Arsenic hyperaccumulation in this plant is an inevitable consequence during phosphate acquisition. Arsenate, arsenite and MMA are transported via the phosphate uptake systems. The co-transport of arsenite/phosphate and MMA/phosphate is reported for the first time in plants. These unique phenomena are useful for understanding arsenic hyperaccumulation and the evolution of this capacity in P. vittata. ^

Occurrence and transformation of organomercury in the Florida Everglades

In this study, a new method was developed based on aqueous phenylation, purge-and-trap preconcentration, gas chromatography (GC) separation, and detection by atomic fluorescence spectrometry (AFS) or inductively coupled plasma mass spectrometry (ICPMS). This technique is suitable for simultaneous determination of trace or ultratrace levels of CH3Hg+ and CH3CH2Hg+ in environmental samples. Method detection limits were 0.03 ng/L for both CH3Hg+ and CH3CH2Hg+ when AFS was used as the detector and 0.02 and 0.01 ng/L for CH3Hg+ and CH 3CH2Hg+ with ICPMS, respectively. The new method has the additional benefits of being free from interference by Cl - and dissolved organic matter. Using the method developed, both CH3Hg+ and CH3CH2Hg+ were detected in a number of soil and sediment samples collected from the Florida Everglades. The identity of CH3CH2Hg+ was verified by purge-and-trap-GC/MS analysis. The possibility of analytical artifact was excluded by using stable isotope tracer technique in combination with ICPMS detection. CH3CH 2Hg+ in the soil samples analyzed was at ng/g level, similar to that of CH3Hg+. The prevalence of CH 3CH2Hg+ in the soil of the Florida Everglades suggests that ethylation plays an important role in the geochemistry of Hg in this wetland. Soil incubation and sawgrass culture experiments using stable isotope tracers revealed that CH3Hg+ was mainly produced by microbial activities under anaerobic conditions, agreeing well with the general understanding of methylation mechanisms of Hg in the environment. Ethylation of Hg was not confirmed in these experiments, indicating that ethylation of Hg most probably follows different mechanisms in comparison to methylation. Further experiments revealed that trace levels of ethyllead species were able to transfer ethyl group to Hg in both deionized water and freshwater matrixes, producing CH3CH2Hg+. This might partially account for the occurrence of CH3CH2Hg+ in the relatively pristine environment of the Florida Everglades.

A multi-method approach for the assessment of composite indices and rankings

There is growing popularity in the use of composite indices and rankings for cross-organizational benchmarking. However, little attention has been paid to alternative methods and procedures for the computation of these indices and how the use of such methods may impact the resulting indices and rankings. This dissertation developed an approach for assessing composite indices and rankings based on the integration of a number of methods for aggregation, data transformation and attribute weighting involved in their computation. The integrated model developed is based on the simulation of composite indices using methods and procedures proposed in the area of multi-criteria decision making (MCDM) and knowledge discovery in databases (KDD). The approach developed in this dissertation was automated through an IT artifact that was designed, developed and evaluated based on the framework and guidelines of the design science paradigm of information systems research. This artifact dynamically generates multiple versions of indices and rankings by considering different methodological scenarios according to user specified parameters. The computerized implementation was done in Visual Basic for Excel 2007. Using different performance measures, the artifact produces a number of excel outputs for the comparison and assessment of the indices and rankings. In order to evaluate the efficacy of the artifact and its underlying approach, a full empirical analysis was conducted using the World Bank's Doing Business database for the year 2010, which includes ten sub-indices (each corresponding to different areas of the business environment and regulation) for 183 countries. The output results, which were obtained using 115 methodological scenarios for the assessment of this index and its ten sub-indices, indicated that the variability of the component indicators considered in each case influenced the sensitivity of the rankings to the methodological choices. Overall, the results of our multi-method assessment were consistent with the World Bank rankings except in cases where the indices involved cost indicators measured in per capita income which yielded more sensitive results. Low income level countries exhibited more sensitivity in their rankings and less agreement between the benchmark rankings and our multi-method based rankings than higher income country groups.

The Geography of Borders: The Method

This text is a first that the author would develop later. It is illustrated with case studies and original terminology. It begins with a brief conceptual contribution on the difference in approach between the German and French geographical schools, and continues with a reflection on the historical and geographical relativity of the boundary. Subsequently, at its greatest extent, the article provides a taxonomy of states: amorphous states, in three cases, that of the "savage peoples" without boundaries, of black Africa; that of semi-civilized peoples of northwest Africa, and the particular case of European civilized nomads, called ―terranovas‖. Framed states, with borders undergoing processes of emergence or extension, especially the case of Yugoslavia. And, in addition, some references to stable boundaries of Albania and the Netherlands

Training proposal in the degree of Master of Early Childhood Education for working the method of historical research in the classroom

Future teachers must be competent in creating educational settings, which provide tools to their students future they can develop a conscious mind, able to interpret their experiences, to make decisions and imagine innovative solutions to help you participate autonomously and responsible in society. This requires an educational system that allows them to integrate the subjective into a broader spatial and temporal context. La patrimonializatión of “Cultural artefacts” and oral history, the basis of which, are found in the active mind and links both the personal and the group experience, don’t only serve as a catalyst to achieving this goal, but rather, they facilitate the implementation of established practice in infant education. To gain this experience we offer the opportunity for students of their degree in Infant Education in the Public University of Navarre, training within the framework of social didactics, allowing students to learn about established practice from iconic, materials and oral sources in the Archive of Intangible Cultural Heritage of Navarra. The vidences points to their effectiveness and presented in a work in progress.

The Ideological Transformation of the Icon Chairman Mao during the Four Modernisations period : As illustrated by "Melody of Youth, Beautiful Soul"

After Chairman Mao's death, in the late 1980's, Mao was removed from official government communications and his iconography transformed from having a specific meaning generation role linked to Maoist ideology, to becoming available for use as a commodity. In this research I use cultural theorist Jacques Derrida's theory of Hauntology and the deconstruction method to analyse a representative Chinese Propaganda poster, "Melody of Youth, Beautiful Soul", in order to ascertain the effect Mao's death had on the Iconography of Chairman Mao, and how Mao is ideologically transformed during this period. Analysing the painting I found specific symbols associated with the iconography of Mao that had been adopted and transformed for the purposes of the CCP. These symbols both suggested the presence of Chairman Mao, as well as negated that presence through being co-opted for other purposes. Using these symbols and writings about the period I deduced that during this period the CCP had to rely on existing symbols of power and authority in order to communicate and legitimise regime change whilst maintaining the semblance of continuity. At the same time they had to decouple these symbols from their original meanings in order to distance themselves from the past and redefine the ideology of China. In the process, Mao's iconography was decoupled from its Maoist ideological heritage and transformed into abstract symbols of power, doctrine and so on. This means that the transformation had made them available to use as an "open basket" into which new, related meanings could be placed – including serving as a commodity.

Introducing the Logarithmic finite element method: a geometrically exact planar Bernoulli beam element

We propose a novel finite element formulation that significantly reduces the number of degrees of freedom necessary to obtain reasonably accurate approximations of the low-frequency component of the deformation in boundary-value problems. In contrast to the standard Ritz–Galerkin approach, the shape functions are defined on a Lie algebra—the logarithmic space—of the deformation function. We construct a deformation function based on an interpolation of transformations at the nodes of the finite element. In the case of the geometrically exact planar Bernoulli beam element presented in this work, these transformation functions at the nodes are given as rotations. However, due to an intrinsic coupling between rotational and translational components of the deformation function, the formulation provides for a good approximation of the deflection of the beam, as well as of the resultant forces and moments. As both the translational and the rotational components of the deformation function are defined on the logarithmic space, we propose to refer to the novel approach as the “Logarithmic finite element method”, or “LogFE” method.

An approximate method for the solution of an influence function foil rolling model

Fleck and Johnson (Int. J. Mech. Sci. 29 (1987) 507) and Fleck et al. (Proc. Inst. Mech. Eng. 206 (1992) 119) have developed foil rolling models which allow for large deformations in the roll profile, including the possibility that the rolls flatten completely. However, these models require computationally expensive iterative solution techniques. A new approach to the approximate solution of the Fleck et al. (1992) Influence Function Model has been developed using both analytic and approximation techniques. The numerical difficulties arising from solving an integral equation in the flattened region have been reduced by applying an Inverse Hilbert Transform to get an analytic expression for the pressure. The method described in this paper is applicable to cases where there is or there is not a flat region.