The one‐inflated positive Poisson mixture model for use in population size estimation

The one‐inflated positive Poisson mixture model (OIPPMM) is presented, for use as the truncated count model in Horvitz–Thompson estimation of an unknown population size. The OIPPMM offers a way to address two important features of some capture–recapture data: one‐inflation and unobserved heterogeneity. The OIPPMM provides markedly different results than some other popular estimators, and these other estimators can appear to be quite biased, or utterly fail due to the boundary problem, when the OIPPMM is the true data‐generating process. In addition, the OIPPMM provides a solution to the boundary problem, by labelling any mixture components on the boundary instead as one‐inflation.     

Translating Predictions of Zoonotic Viruses for Policymakers

Recent outbreaks of Ebola virus disease and Zika virus disease highlight the need for disseminating accurate predictions of emerging zoonotic viruses to national governments for disease surveillance and response. Although there are published maps for many emerging zoonotic viruses, it is unknown if there is agreement among different models or if they are concordant with national expert opinion. Therefore, we reviewed existing predictions for five high priority emerging zoonotic viruses with national experts in Cameroon to investigate these issues and determine how to make predictions more useful for national policymakers. Predictive maps relied primarily on environmental parameters and species distribution models. Rift Valley fever virus and Crimean-Congo hemorrhagic fever virus predictions differed from national expert opinion, potentially because of local livestock movements. Our findings reveal that involving national experts could elicit additional data to improve predictions of emerging pathogens as well as help repackage predictions for policymakers.     

Quantifying the Role of Nanotubes in Nano:Nano Composite Supercapacitor Electrodes

Many promising supercapacitor electrode materials have high resistivity and require conductive additives to function effectively. However, the detailed role of the additive is not understood. Here, this question is resolved by applying a quantitative model for resistance‐limited supercapacitor electrodes to Co(OH)₂‐nanosheet/carbon nanotube composites. Without nanotubes, theory predicts and experiments show that while the low‐rate capacitance increases linearly with electrode thickness, the high rate capacitance decreases with thickness due to slow charging. Experiments supported by theory show that nanotube addition has two effects. First, the nanotube network effectively distributes charge, increasing the intrinsic electrode performance to the limit associated with its accessible surface area. Second, at high‐rate, the increased electrode conductivity shifts the rate‐limiting resistance from electrode to electrolyte, thus removing the thickness‐dependent capacitance falloff. Furthermore, the analysis quantifies the out‐of‐plane conductivity of the nanotube network, identifies the cross‐over from resistance‐limited to diffusion‐limited behavior, and allows full electrode modeling, facilitating rational design.     

A modern view of phenylalanine ammonia lyase.

Phenylalanine ammonia lyase (PAL; E.C.4.3.1.5), which catalyses the biotransformation of L-phenylalanine to trans-cinnamic acid and ammonia, was first described in 1961 by Koukol and Conn. Since its discovery, much knowledge has been gathered with reference to the enzyme's catabolic role in microorganisms and its importance in the phenyl propanoid pathway of plants. The 3-dimensional structure of the enzyme has been characterized using X-ray crystallography. This has led to a greater understanding of the mechanism of PAL-catalyzed reactions, including the discovery of a recently described cofactor, 3,5-dihydro-5-methyldiene-4H-imidazol-4-one. In the past 3 decades, PAL has gained considerable significance in several clinical, industrial, and biotechnological applications. The reversal of the normal physiological reaction can be effectively employed in the production of optically pure L-phenylalanine, which is a precursor of the noncalorific sweetener aspartame (L-phenylalanyl-L-aspartyl methyl ester). The enzyme's natural ability to break down L-phenylalanine makes PAL a reliable treatment for the genetic condition phenylketonuria. In this mini-review, we discuss prominent details relating to the physiological role of PAL, the mechanism of catalysis, methods of determination and purification, enzyme kinetics, and enzyme activity in nonaqueous media. Two topics of current study on PAL, molecular biology and crystal structure, are also discussed.     

Growing colorectal tumors: minimizing microbial and stromal competition and assessing in vitro selection pressures

Development of primary colorectal cancer cell lines ishampered by contamination from regional microbes, overgrowthof stromal cells, and purported genetic drift from selectionpressures in vitro. We initiated 32 primaryadenocarcinomas, 3 recurrences and 6 distant metastases incell culture. Twelve cell lines from eleven tumors weregenerated (26.8%) overall. Nine of 32 primary tumorsyielded 10 cell lines, 5 were lost to contamination, 13 wereoverwhelmed by stromal cells, and 5 demonstrated no growth.Addition of isobutyl methyl xanthine (IBMX) to culturelimited fibroblastoid growth. There was no associationbetween tumor location (p = 0.535, mid-P), degree ofdifferentiation (p = 0.850, mid-P) or clinicopathologic stage(p = 0.400, mid-P), and the ability of cells to becomeestablished in culture. The majority of cell lines hadsimilar nuclear DNA content and expression of cell-surfaceantigens compared with their parent tumors. Microbialcontamination and stromal cell overgrowth present thegreatest obstacle to capturing a representative bank ofcolon tumors in vitro.