Bioagent Sample Matching using Elemental Composition Data: an Approach to Validation

Sample matching is a fundamental capability that can have high probative value in a forensic context if proper validation studies are performed. In this report we discuss the potential utility of using the elemental composition of two bioagent samples to decide if they were produced in the same batch, or by the same process. Using guidance from the recent NRC study of bullet lead analysis and other sources, we develop a basic likelihood ratio framework for evaluating the evidentiary weight of elemental analysis data for sample matching. We define an objective metric for comparing two samples, and propose a method for constructing an unbiased population of test samples. We illustrate the basic methodology with some existing data on dry Bacillus thuringiensis preparations, and outline a comprehensive plan for experimental validation of this approach

Resolution in forensic microbial genotyping

Resolution is a key parameter for differentiating among the large number of strain typing methods that could be applied to pathogens involved in bioterror events or biocrimes. In this report we develop a first-principles analysis of strain typing resolution using a simple mathematical model to provide a basis for the rational design of microbial typing systems for forensic applications. We derive two figures of merit that describe the resolving power and phylogenetic depth of a strain typing system. Rough estimates of these figures-of-merit for MLVA, MLST, IS element, AFLP, hybridization microarrays, and other bacterial typing methods are derived from mutation rate data reported in the literature. We also discuss the general problem of how to construct a ''universal'' practical typing system that has the highest possible resolution short of whole-genome sequencing, and that is applicable with minimal modification to a wide range of pathogens

A validation framework for microbial forensic methods based on statistical pattern recognition

This report discusses a general approach to validating microbial forensic methods that attempt to simultaneously distinguish among many hypotheses concerning the manufacture of a questioned biological agent sample. It focuses on the concrete example of determining growth medium from chemical or molecular properties of a bacterial agent to illustrate the concepts involved

Frequency agile OPO-based transmitters for multiwavelength DIAL

We describe a first generation mid-infrared transmitter with pulse-to- pulse frequency agility and both wide and narrow band capability. This transmitter was used to make multicomponent DIAL measurements in the field

Refractive Index of Humid Air in the Infrared: Model Fits

The theory of summation of electromagnetic line transitions is used to tabulate the Taylor expansion of the refractive index of humid air over the basic independent parameters (temperature, pressure, humidity, wavelength) in five separate infrared regions from the H to the Q band at a fixed percentage of Carbon Dioxide. These are least-squares fits to raw, highly resolved spectra for a set of temperatures from 10 to 25 C, a set of pressures from 500 to 1023 hPa, and a set of relative humidities from 5 to 60%. These choices reflect the prospective application to characterize ambient air at mountain altitudes of astronomical telescopes.Comment: Corrected exponents of c0ref, c1ref and c1p in Table

Influence and measurement of mass ablation in ICF implosions

Point design ignition capsules designed for the National Ignition Facility (NIF) currently use an x-ray-driven Be(Cu) ablator to compress the DT fuel. Ignition specifications require that the mass of unablated Be(Cu), called residual mass, be known to within 1% of the initial ablator mass when the fuel reaches peak velocity. The specifications also require that the implosion bang time, a surrogate measurement for implosion velocity, be known to +/- 50 ps RMS. These specifications guard against several capsule failure modes associated with low implosion velocity or low residual mass. Experiments designed to measure and to tune experimentally the amount of residual mass are being developed as part of the National Ignition Campaign (NIC). Tuning adjustments of the residual mass and peak velocity can be achieved using capsule and laser parameters. We currently plan to measure the residual mass using streaked radiographic imaging of surrogate tuning capsules. Alternative techniques to measure residual mass using activated Cu debris collection and proton spectrometry have also been developed. These developing techniques, together with bang time measurements, will allow us to tune ignition capsules to meet NIC specs

Community-curated and standardised metadata of published ancient metagenomic samples with AncientMetagenomeDir

Ancient DNA and RNA are valuable data sources for a wide range of disciplines. Within the field of ancient metagenomics, the number of published genetic datasets has risen dramatically in recent years, and tracking this data for reuse is particularly important for large-scale ecological and evolutionary studies of individual microbial taxa, microbial communities, and metagenomic assemblages. AncientMetagenomeDir (archived at https://doi.org/10.5281/zenodo.3980833) is a collection of indices of published genetic data deriving from ancient microbial samples that provides basic, standardised metadata and accession numbers to allow rapid data retrieval from online repositories. These collections are community-curated and span multiple sub-disciplines in order to ensure adequate breadth and consensus in metadata definitions, as well as longevity of the database. Internal guidelines and automated checks to facilitate compatibility with established sequence-read archives and term-ontologies ensure consistency and interoperability for future meta-analyses. This collection will also assist in standardising metadata reporting for future ancient metagenomic studies.Competing Interest StatementThe authors have declared no competing interest.Background & Summary Methods - Repository Structure - Data Acquisition - Data Validation Data Records Technical Validation Usage Note