Mark D. Ginsberg

Modeling Pressure-Driven Transport of Proteins Through a Nanochannel

Reducing the size of a nanofluidic channel not only creates new opportunities for high-precision manipulation of biological macromolecules but also makes the performance of the entire nanofluidic system more susceptible to undesirable interactions between the transported biomolecules and the walls of the channel. In this paper, we report molecular dynamics simulations of pressure-driven flow through a silica nanochannel and characterize, with atomic resolution, adsorption of a model protein to the surface of the nanochannel. Although the simulated adsorption of the proteins was found to be nonspecific, it had a dramatic effect on the rate of the protein transport. To determine the relative strength of the protein-silica interactions in different adsorbed states, we simulated flow-induced desorption of the proteins from the silica surface. Our analysis of the protein conformations in the adsorbed states did not reveal any simple dependence of the adsorption strength on the size and composition of the protein-silica contact, suggesting that the heterogeneity of the silica surface may be an important factor.

Landmine detection using feedback NQR

Nuclear quadrupole resonance (NQR) is well suited for detecting land mines with non-metallic cases. It provides both spatial localization and chemical identification of explosives. A search coil produces a train of radio frequency (RF) magnetic pulses that perturb the orientation of nitrogen nuclei contained within the explosive material. Following each RF pulse, the nuclei rotate back to orientations of lower energy. As the nitrogen nuclei possess a magnetic moment, their motion following an RF pulse induces a detectable voltage in the search coil. The NQR signal strength depends on the amplitude, frequency, duration and repetition rate of the applied RF pulses. The optimal selection of RF parameters requires knowledge that is not available in practice, such as the location of the explosive with respect to the search coil. Existing NQR detection systems sacrifice signal intensity by using field pulse parameters. We demonstrate that feedback control provides a means for automatically adjusting multiple pulse parameters so that the maximum NQR signal strength is obtained. The advantages afforded to landmine detection using feedback NQR are summarized.

A case study in bio-inspired engineering design: defense applications of exoskeletal sensors

As part of a bio-inspired design process, the authors examine exoskeletal sensors found in insects and their potential application to armor and hardened buildings. In this way, the outer hardening of a structure or vehicle would not limit the ability of occupants to arrive at an actionable picture of the outer environment. To this end, various sensor modalities employed by insects are compared and contrasted with their current human-engineered equivalents. In several sensing modalities, biosensors perform better, are smaller, and more energy efficient than human-engineered equivalents. They note that biological designs tend to employ non-linear response to signal amplitude and respond with heightened sensitivity over a greater dynamic range of signals than human-engineered sensors. The insect biological sensors have structural and mechanical innovations that preserve the protective capacity of the exoskeleton.

Bench-scale aerosol filtration test system and evaluation of an acoustic bioaerosol removal device for indoor air streams

It is important to have well-defined, reproducible methods to evaluate and compare newly developed air filtration equipment. To facilitate accurate assessment of air purification devices at the bench scale, an experimental system was designed, built, and documented to evaluate particulate removal efficiency (PRE) of air filtration devices based on principles used in ASHRAE standards. The system was then carefully characterized and used to evaluate PRE and total energy consumption of a novel acoustically enhanced impaction (AEI) air purification device. The AEI device demonstrated 99.998% PRE of 0.5–1.5 μm diameter KCl particles while causing a 120 Pa pressure drop and requiring a total of 3.0 W/l of air treated at indoor ambient conditions. A single element of the AEI device operated in a biological safety level 2 facility was then used to evaluate PRE of bioaerosol consisting of Bacillus cereus (BC) spores. PRE of BC was 99.86 ± 0.05% at indoor ambient temperature and pressure. This research describes the use of the Bench-scale Air Purification Testing and Evaluation Chamber (BAP-TEC) to experimentally evaluate and compare PRE and total energy requirements of novel air purification devices at the bench scale (280–1400 alpm). Further, an AEI device containing a fibrous filter media and high intensity sound field in the same control volume is evaluated using the BAP-TEC. Temporally resolved PRE of a bioaerosol by the AEI is also presented. Copyright 2013 American Association for Aerosol Research

Bioprotection of facilities

The anthrax attacks of 2001 energized research directed toward reducing health consequences from airborne contaminants by augmenting current heating ventilation and air-conditioning (HVAC) systems. Even during peacetime, interest will continue in improving HVAC components to reduce biocontaminants associated with sick building syndrome. Current HVAC design uses numerical simulation methods of ordinary differential equations to predict approximate performance. The authors show that state-space Laplace Transform calculations actually solve the underlying differential equations and yield algebraic expressions that provide new insight. To sharpen the arguments in favor of this methodology, attention is restricted to improving existing HVAC systems to increase protection from an external release of hazardous particulates. By nearly eliminating the need for dynamical simulation, the resulting methods can be applied to far more complex HVAC designs with little additional computational effort. The new methods reduce the time required for computation by three orders of magnitude. These algebraic methods also can be extended to disparate technical problems including internal particulate release, gas masks, and designing new protective buildings.

Water flow and distribution around buried landmines

Soil properties make a significant impact in the observed responses of various sensors for mine detection. Soil moisture affects the performance of electromagnetic sensors through its effects on soil thermal and dielectric properties. We have initiated laboratory, field and numerical studies to advance our fundamental understanding of the properties and governing processes of moisture distribution and flow around buried landmines. The laboratory component features magnetic resonance imaging (MRI) to map water distribution around a mine-like obstacle placed in a test soil sample. The field component investigates the moisture migration around landmines under realistic weather and soil conditions. We use anti-tank mines instrumented with moisture and temperature sensors to monitor the weather-driven processes. The numerical component investigates existing physics models underlying current simulations of moisture transport in soils. We use existing flow simulators to evaluate the completeness of process descriptions and to estimate the relative importance of individual processes on micro-scale moisture movement. These existing simulators include both continuum codes designed to work at scales much larger than the grain size and pore-scale models that discretize individual pores. We present the preliminary results of our investigations and discuss the potential impact of our findings on infrared and radar detection of buried landmines.

H 2 0Fate—New Software for Fate and Transport Simulations in Water Distribution Systems

BlazeTech has recently developed the H 2 OFate software to predict the fate and transport of residual disinfectants and chemical and biological contaminants in water distribution systems. This software accounts for the reactions of contaminants and residual disinfectant with each other (in bulk water and at the pipe wall) and their adhesion/reactions with the pipe walls. We have developed this software using EPANET-MSX as the platform by adding the necessary phenomenology, data visualization tools and reaction kinetics for over 60 bacteria, viruses, toxins and chemical agents. Using H 2 OFate we carried out parametric calculations for simulated contaminant release into a sample water distribution network. We have examined the effects of initial contaminant concentration, and water quality parameters such as residual total free chlorine (TFC) concentration and temperature on the spatial and temporal evolution of hazard in the network. These calculations have shown that increasing the residual disinfectant concentration and lowering the pH are potential strategies to minimize the contamination hazard in the network. This paper describes the H 2 OFate software and the results from the above parametric calculations.

Prediction of contaminant fate and transport in potable water systems using H2OFate

BlazeTech has recently developed a software called H2OFate to predict the fate and transport of chemical and biological contaminants in water distribution systems. This software includes models for the reactions of these contaminants with residual disinfectant in bulk water and at the pipe wall, and their adhesion/reactions with the pipe walls. This software can be interfaced with sensors through SCADA systems to monitor water distribution networks for contamination events and activate countermeasures, as needed. This paper presents results from parametric calculations carried out using H2OFate for a simulated contaminant release into a sample water distribution network.

Terrorism and security of water distribution systems: A primer

In the post-9/11 environment, the anthrax attacks of 18 September 2001 re-energized several aspects of water security research. In the private sector, there was a resurgence of interest in transportable water treatment devices and in developing sensor technology to identify contaminants in water. Government scientists and engineers became interested in improving the current understanding of fate and transport of contaminants in water distribution systems and in developing water treatment and cleanup technology that did not generate hazardous waste. This paper is organized in two broad parts. First there is an overview of a generic water distribution system sufficient to highlight the system’s vulnerabilities, common misperceptions about attacks and how to respond, and an overview of available decontamination methods. With this background information available, we then present basic discussions about likely attack scenarios, remaining problems with current models of fate and transport of contaminants in a distribution system, and areas of current research.