Revealing Relationships among Relevant Climate Variables with Information Theory

A primary objective of the NASA Earth-Sun Exploration Technology Office is to understand the observed Earth climate variability, thus enabling the determination and prediction of the climate's response to both natural and human-induced forcing. We are currently developing a suite of computational tools that will allow researchers to calculate, from data, a variety of information-theoretic quantities such as mutual information, which can be used to identify relationships among climate variables, and transfer entropy, which indicates the possibility of causal interactions. Our tools estimate these quantities along with their associated error bars, the latter of which is critical for describing the degree of uncertainty in the estimates. This work is based upon optimal binning techniques that we have developed for piecewise-constant, histogram-style models of the underlying density functions. Two useful side benefits have already been discovered. The first allows a researcher to determine whether there exist sufficient data to estimate the underlying probability density. The second permits one to determine an acceptable degree of round-off when compressing data for efficient transfer and storage. We also demonstrate how mutual information and transfer entropy can be applied so as to allow researchers not only to identify relations among climate variables, but also to characterize and quantify their possible causal interactions.Comment: 14 pages, 5 figures, Proceedings of the Earth-Sun System Technology Conference (ESTC 2005), Adelphi, M

Individual bacterial cells can use spatial sensing of chemical gradients to direct chemotaxis on surfaces

Swimming bacteria navigate chemical gradients using temporal sensing to detect changes in concentration over time. Here we show that surface-attached bacteria use a fundamentally different mode of sensing during chemotaxis. We combined microfluidic experiments, massively parallel cell tracking and fluorescent reporters to study how Pseudomonas aeruginosa senses chemical gradients during pili-based ‘twitching’ chemotaxis on surfaces. Unlike swimming cells, we found that temporal changes in concentration did not induce motility changes in twitching cells. We then quantified the chemotactic behaviour of stationary cells by following changes in the sub-cellular localization of fluorescent proteins as cells are exposed to a gradient that alternates direction. These experiments revealed that P. aeruginosa cells can directly sense differences in concentration across the lengths of their bodies, even in the presence of strong temporal fluctuations. Our work thus overturns the widely held notion that bacterial cells are too small to directly sense chemical gradients in space

Cerebrospinal fluid levels of extracellular heat shock protein 72: A potential biomarker for bacterial meningitis in children

Extracellular heat shock protein 72 (Hsp72) is an endogenous danger signal and potential biomarker for critical illness in children. We hypothesized that elevated levels of extracellular Hsp72 in the cerebrospinal fluid (CSF) of children with suspected meningitis could predict bacterial meningitis. We measured extracellular Hsp72 levels in the CSF of 31 critically ill children with suspected meningitis via a commercially available enzyme-linked immunosorbent assay. Fourteen had bacterial meningitis based on CSF pleocytosis and bacterial growth in either blood or CSF culture. Seventeen children with negative cultures comprised the control group. CSF Hsp72 was significantly elevated in children with bacterial meningitis compared to controls. Importantly, CSF Hsp72 levels did not correlate with the CSF white blood cell count. On receiver operator characteristic analysis, using a cut-off of 8.1 ng/mL, CSF Hsp72 has a sensitivity of 79% and a specificity of 94% for predicting bacterial meningitis. We therefore conclude that CSF extracellular Hsp72 levels are elevated in critically ill children with bacterial meningitis versus controls. Hsp72 potentially offers clinicians improved diagnostic information in distinguishing bacterial meningitis from other processes

Mitochondrial Intergenic Spacer in Fairy Basslets (Serranidae: Anthiinae) and the Simultaneous Analysis of Nucleotide and Rearrangement Data

We present the results of a study that implements a recently developed phylogenetic algorithm that combines fixed-states nucleotide optimization with breakpoint analysis to identify and examine the evolution of a mitochondrial intergenic spacer between the tRNAVal and 16S rRNA loci in a clade of fairy basslets (Serranidae: Anthiinae). The results of the analysis indicate that this spacer evolved once and that it may be increasing in size through evolutionary time. The resulting molecular hypothesis corroborates much of the previous morphological phylogenetic work.We would like to thank J. Smith (Los Alamos National Laboratory) and J. Faivovich, T. Grant, K. Pickett, J. Sparks, M. Stiassny, and K. Tang (all at or formerly at the American Museum of Natural History [AMNH]) for discussing aspects of this project with us. We are grateful to H. Endo (Kochi University), the Gahan Family, J. Leis and M. McGrouther (Australian Museum), Reef and Fin (Stamford, CT), and H. Walker (Scripps Institution of Oceanography) for providing specimens used in this study. This project was supported by funding from the AMNH Lerner-Gray Program for Marine Research, the NASA–Ames Fundamental Space Biology Program, the Field Museum of Natural History, and the National Science Foundation (DEB-0405246 and DEB-0732642)

A comparison of sex offenders and other types of offenders referred to intellectual disability forensic services

This study compared 131 sex offenders with ID and 346 other types of offenders with ID using case file records. All the females in the study were non sexual offenders. Significantly more sexual offenders were referred from court and criminal justice services while significantly fewer were referred from secondary healthcare. A higher percentage of sex offenders had some form of legal status at time of referral. Greater proportions of non sexual offenders were referred for aggression, damage to property, substance abuse and fire setting while only the sex offenders had an index sex offence. For previous offending, the non sexual offenders had higher rates of aggression, cruelty and neglect of children, property damage and substance abuse while the sexual offenders had higher rates of previous sexual offending. For psychiatric disturbance and adversity in childhood, only ADHD showed a significant difference between groups with the non sexual offenders recording higher rates

Oxidation chemistry of d^0 organometallic complexes

Electron-transfer processes can play an important role in organometallic chemistry. Herein, we demonstrate that even d^0 organometallic complexes exhibit a rich redox chemistry and present electrochemical, kinetics, and stereochemical studies that establish a general outer-sphere oxidation process for d^0 group 4 metallocene complexes. This oxidation chemistry closely parallels the reported LMCT photochemistry of these complexes

Modeling Reactive Wetting when Inertial Effects are Dominant

Recent experimental studies of molten metal droplets wetting high temperature reactive substrates have established that the majority of triple-line motion occurs when inertial effects are dominant. In light of these studies, this paper investigates wetting and spreading on reactive substrates when inertial effects are dominant using a thermodynamically derived, diffuse interface model of a binary, three-phase material. The liquid-vapor transition is modeled using a van der Waals diffuse interface approach, while the solid-fluid transition is modeled using a phase field approach. The results from the simulations demonstrate an O \left( t^{-\nicefrac{1}{2}} \right) spreading rate during the inertial regime and oscillations in the triple-line position when the metal droplet transitions from inertial to diffusive spreading. It is found that the spreading extent is reduced by enhancing dissolution by manipulating the initial liquid composition. The results from the model exhibit good qualitative and quantitative agreement with a number of recent experimental studies of high-temperature droplet spreading, particularly experiments of copper droplets spreading on silicon substrates. Analysis of the numerical data from the model suggests that the extent and rate of spreading is regulated by the spreading coefficient calculated from a force balance based on a plausible definition of the instantaneous interface energies. A number of contemporary publications have discussed the likely dissipation mechanism in spreading droplets. Thus, we examine the dissipation mechanism using the entropy-production field and determine that dissipation primarily occurs in the locality of the triple-line region during the inertial stage, but extends along the solid-liquid interface region during the diffusive stage