INLA or MCMC? A Tutorial and Comparative Evaluation for Spatial Prediction in log-Gaussian Cox Processes

We investigate two options for performing Bayesian inference on spatial log-Gaussian Cox processes assuming a spatially continuous latent field: Markov chain Monte Carlo (MCMC) and the integrated nested Laplace approximation (INLA). We first describe the device of approximating a spatially continuous Gaussian field by a Gaussian Markov random field on a discrete lattice, and present a simulation study showing that, with careful choice of parameter values, small neighbourhood sizes can give excellent approximations. We then introduce the spatial log-Gaussian Cox process and describe MCMC and INLA methods for spatial prediction within this model class. We report the results of a simulation study in which we compare MALA and the technique of approximating the continuous latent field by a discrete one, followed by approximate Bayesian inference via INLA over a selection of 18 simulated scenarios. The results question the notion that the latter technique is both significantly faster and more robust than MCMC in this setting; 100,000 iterations of the MALA algorithm running in 20 minutes on a desktop PC delivered greater predictive accuracy than the default \verb=INLA= strategy, which ran in 4 minutes and gave comparative performance to the full Laplace approximation which ran in 39 minutes.Comment: This replaces the previous version of the report. The new version includes results from an additional simulation study, and corrects an error in the implementation of the INLA-based method

The Human Capital “Impact” on E-Business: The Case of Encyclopedia Britannica

[Excerpt] The term “New Economy” has been coined to describe the remarkable economic performance of the 1990s. Stiroh, (1999) an economist at the Federal Reserve Bank of New York observes that its defining characteristic is a “focus on increasing globalization and expanding information technology” (pg. 87). Research suggests that revenues from electronic based business to business trade will double over the next five years from $43 billion in 1998 to$1.3 trillion in 2003. Revenues from business to consumer trade are predicted to rise from $8 billion to$108 billion over the same time period (Forrester Research, 1998). However, there is increasing attention to the challenges facing business in the new economy, and an increasing chorus of analysts suggesting how tenuous many of these business models really are. A recent Barron’s article showed that many dot-com companies have only days of remaining cash (Willoughby, March 20, 1999). Such a key emerging phenomenon has not escaped the attention of writers, though the existing body of writing has some important gaps. We would classify existing e-business literature into two groups. First, there is a growing body of literature that discusses the how the Internet is transforming business models and organizational strategies. A second, much smaller body of work has focused on e-HR, or more specifically, the implications of the Internet on various HR practices

Vocal Classification of Vocalizations of a Pair of Asian Small-Clawed Otters to Determine Stress

Asian Small-Clawed Otters (Aonyx cinerea) are a small, protected but threatened species living in freshwater. They are gregarious and live in monogamous pairs for their lifetimes, communicating via scent and acoustic vocalizations. This study utilized a hidden Markov model (HMM) to classify stress versus non-stress calls from a sibling pair under professional care. Vocalizations were expertly annotated by keepers into seven contextual categories. Four of these—aggression, separation anxiety, pain, and prefeeding—were identified as stressful contexts, and three of them—feeding, training, and play—were identified as non-stressful contexts. The vocalizations were segmented, manually categorized into broad vocal type call types, and analyzed to determine signal to noise ratios. From this information, vocalizations from the most common contextual categories were used to implement HMM-based automatic classification experiments, which included individual identification, stress vs non-stress, and individual context classification. Results indicate that both individual identity and stress vs non-stress were distinguishable, with accuracies above 90%, but that individual contexts within the stress category were not easily separable

First measurement of gravitational lensing by cosmic voids in SDSS

We report the first measurement of the diminutive lensing signal arising from matter underdensities associated with cosmic voids. While undetectable individually, by stacking the weak gravitational shear estimates around 901 voids detected in SDSS DR7 by Sutter et al. (2012a), we find substantial evidence for a depression of the lensing signal compared to the cosmic mean. This depression is most pronounced at the void radius, in agreement with analytical models of void matter profiles. Even with the largest void sample and imaging survey available today, we cannot put useful constraints on the radial dark-matter void profile. We invite independent investigations of our findings by releasing data and analysis code to the public at https://github.com/pmelchior/void-lensingComment: 6 pages, 5 figures, as accepted by MNRA

Detecting range expansions from genetic data

We propose a method that uses genetic data to test for the occurrence of a recent range expansion and to infer the location of the origin of the expansion. We introduce a statistic for pairs of populations $\psi$ (the directionality index) that detects asymmetries in the two-dimensional allele frequency spectrum caused by the series of founder events that happen during an expansion. Such asymmetry arises because low frequency alleles tend to be lost during founder events, thus creating clines in the frequencies of surviving low-frequency alleles. Using simulations, we further show that $\psi$ is more powerful for detecting range expansions than both $F_{ST}$ and clines in heterozygosity. We illustrate the utility of $\psi$ by applying it to a data set from modern humans and show how we can include more complicated scenarios such as multiple expansion origins or barriers to migration in the model

Pottery traditions, consumers' choices and exchange networks at Late Bronze Age Cobatillas la Vieja (southeast Iberia)

Cobatillas la Vieja is one of the main settlements for understanding the beginning of the Late Bronze Age (14th-13th centuries cal. BC) in the southeast of the Iberian Peninsula. After the macroscopic study of their ceramic assemblage, 30 representative samples were analysed by thin-section petrography, X-ray diffraction (XRD), scanning electron microscopy (SEM) and binocular microscopy to address issues of provenance and technology. The characterization of four different fabric groups and several individuals reveals a more complex picture of production traditions, pottery exchange and consumption than often assumed for this period of supposed recession and socio-cultural transition. Potters' choices in different production locations are discussed, with an examination on the nature of consumption in two households that suggest both regional and inter-regional exchange of ceramics in the Late Bronze Age.Peer reviewe

solvation by a polar aprotic solvent

A series of strong H-bonded complexes of trimethylglycine, also known as betaine, with acetic, chloroacetic, dichloroacetic, trifluoroacetic and hydrofluoric acids as well as the homo-conjugated cation of betaine with trifluoroacetate as the counteranion were investigated by low-temperature (120–160 K) liquid-state NMR spectroscopy using CDF3/CDF2Cl mixture as the solvent. The temperature dependencies of 1H NMR chemical shifts are analyzed in terms of the solvent–solute interactions. The experimental data are explained assuming the combined action of two main effects. Firstly, the solvent ordering around the negatively charged OHX region of the complex (X = O, F) at low temperatures, which leads to a contraction and symmetrisation of the H-bond; this effect dominates for the homo-conjugated cation of betaine. Secondly, at low temperatures structures with a larger dipole moment are preferentially stabilized, an effect which dominates for the neutral betaine–acid complexes. The way this second contribution affects the H-bond geometry seems to depend on the proton position. For the Be+COO−⋯HOOCCH3 complex (Be = (CH3)3NCH2–) the proton displaces towards the hydrogen bond center (H-bond symmetrisation, O⋯O contraction). In contrast, for the Be+COOH⋯−OOCCF3 complex the proton shifts further away from the center, closer to the betaine moiety (H-bond asymmetrisation, O⋯O elongation). Hydrogen bond geometries and their changes upon lowering the temperature were estimated using previously published H-bond correlations